Electrochemical energy storage devices

ABSTRACT

Provided herein are energy storage devices. In some cases, the energy storage devices are capable of being transported on a vehicle and storing a large amount of energy. An energy storage device is provided comprising at least one liquid metal electrode, an energy storage capacity of at least about 1 MWh and a response time less than or equal to about 100 milliseconds (ms).

CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.16/592,621, filed Oct. 3, 2019, which is a continuation-in-partapplication of U.S. patent application Ser. No. 15/647,468 (now U.S.Pat. No. 10,541,451), filed Jul. 12, 2017, which is acontinuation-in-part application of U.S. patent application Ser. No.14/688,179 (now U.S. Pat. No. 9,735,450), filed Apr. 16, 2015, which isa continuation of PCT Application No. PCT/US2013/065092, filed Oct. 15,2013, which claims the benefit of U.S. Provisional Application No.61/715,821, filed Oct. 18, 2012, and which is a continuation-in-part ofU.S. patent application Ser. No. 13/801,333 (now U.S. Pat. No.9,312,522), filed Mar. 13, 2013, which claims the benefit of U.S.Provisional Application No. 61/763,925, filed Feb. 12, 2013, and U.S.Provisional Application No. 61/715,821, filed Oct. 18, 2012, and whichis a continuation-in-part of U.S. patent application Ser. No. 14/536,563(now U.S. Pat. No. 9,728,814), filed Nov. 7, 2014, which is acontinuation of U.S. patent application Ser. No. 14/178,806 (now U.S.Pat. No. 9,520,618), filed Feb. 12, 2014, which claims the benefit ofU.S. Provisional Application No. 61/763,925, filed Feb. 12, 2013, eachof which is entirely incorporated herein by reference, and is acontinuation-in-part application of U.S. patent application Ser. No.15/140,434, filed Apr. 27, 2016, which is a continuation of PCTApplication No. PCT/US2014/063222, filed Oct. 30, 2014, and which claimsthe benefit of U.S. Provisional Application No. 61/898,642, filed Nov.1, 2013.

Various devices are configured for use at elevated or high temperatures.Examples of such devices include energy storage devices, such as, forexample, elevated or high temperature batteries (e.g., comprising liquidmetal electrodes), which are devices capable of converting storedchemical energy into electrical energy. Such devices may in some casesoperate at a temperature of, or in excess of, 300° C. Energy storagedevices (e.g., batteries) may be used within an electric power grid oras part of a standalone system. Batteries may be used in many householdand industrial applications. Batteries can be charged from an electricpower source (e.g., electric power produced by a renewable energyresource such as wind or solar) for later discharge when there is ademand for electrical energy consumption.

SUMMARY

Recognized herein are various limitations associated with elevated orhigh temperature devices, such as, for example, battery systems (also“batteries” herein). For instance, some battery systems operate at hightemperatures (e.g., at least about 100° C. or 300° C.) and comprisereactive materials (e.g., reactive metal vapors of lithium, sodium,potassium, magnesium, or calcium). Operation of such batteries cangenerate heat that may need to be removed from the system to maintain astable operating temperature. In some cases, such as, for example, whenthe battery is idle, heat is not generated and needs to be added to thesystem to maintain the battery at a given operating state (e.g., tomaintain electrodes and/or electrolyte in a molten state).

The present disclosure provides energy storage systems, and systems andmethods for operating energy storage systems. Operation (e.g., heatmanagement or temperature control) of an energy storage system mayinclude providing a thermal management fluid to or from the energystorage system. In some cases, the thermal management fluid may beprovided to (e.g., contacted with) the energy storage system as well aswith other portions of the system (e.g., a storage reservoir, condenseror other component in the system). The thermal management fluid maycontact one or more portions of the energy storage system. For example,the systems and methods herein can flow the thermal management fluidthrough a frame of the energy storage system to maintain the system atan operating temperature, operate the system in an energy-efficientmanner, extend an operating lifetime of the system and/or enable thesystem to operate during periods (e.g., time periods, or periods with agiven supply and/or demand level) when it can supply most value (e.g.,maximum profit (value) can be derived from operation of the system) tothe customer (e.g., discharge during hours of peak energy demand).

In an aspect of the present disclosure, an energy storage systemcomprises a plurality of electrochemical cells each comprising anegative electrode, electrolyte and positive electrode, wherein at leastone, two, or all of the negative electrode, the electrolyte and thepositive electrode is in a liquid state at an operating temperature ofthe electrochemical cell, wherein the plurality of electrochemical cellsare connected in series and/or parallel; and a frame supporting theplurality of electrochemical cells, wherein the frame comprises one ormore fluid flow paths for bringing a thermal management fluid in thermalcommunication with at least a subset of the plurality of electrochemicalcells.

In an embodiment, the frame comprises tubes, pipes, or enclosed trusses.In another embodiment, the thermal management fluid is air, a gas, oil,molten salt, water, or steam. In another embodiment, the gas is argon ornitrogen. In another embodiment, the operating temperature is betweenabout 150° C. and 750° C. In another embodiment, the system furthercomprises thermal insulation surrounding the frame elements. In anotherembodiment, the thermal insulation enables the system to operatecontinuously in a self-heated configuration when charged and/ordischarged at least once every two days. In another embodiment, in aself-heated configuration, the thermal insulation enables the system toincrease its internal temperature above the operating temperature duringregular operation, and wherein the system maintains its internaltemperature at about the operating temperature by activating an actuatorto allow the thermal management fluid to flow through the one or morefluid flow paths driven by natural convection.

In an embodiment, the system further comprises insulation along at leasta portion of the fluid flow path to aid in removal of heat from apredetermined location within the system. In another embodiment, theinsulation is thinner in a portion of the fluid flow path adjacent aheated zone of the system.

In an embodiment, the thermal management fluid does not contact theelectrochemical cells. In another embodiment, the framemechanically/structurally supports the electrochemical cells in a seriesand/or parallel configuration. In another embodiment, the frame isresistant to corrosion. In another embodiment, the frame comprisesstainless steel. In another embodiment, the frame is chemicallyresistant to the thermal management fluid. In another embodiment, theframe is chemically resistant to reactive metals. In another embodiment,the system further comprises a fluid flow system that is configured andarranged to direct the thermal management fluid through the one or morefluid flow paths of the frame. In another embodiment, the fluid flowsystem is configured or programmed to provide the thermal managementfluid at an adjustable flow rate that is selected to maintain thetemperature of the system at the operating temperature. In anotherembodiment, the system comprises at least 10 electrochemical cells. Inanother embodiment, the frame comprises a chamber that contains at leasta subset of the plurality of electrochemical cells. In anotherembodiment, at least a subset of the plurality of electrochemical cellsis connected in series.

In an embodiment, the frame comprises a plurality of parallel fluid flowpaths. In another embodiment, fluid flow rates through at least two ofthe parallel fluid flow paths are separately controllable. In anotherembodiment, the frame comprises a plurality of orthogonal fluid flowpaths. In another embodiment, the frame is rectangular box. In anotherembodiment, a dimension of the frame is configured to selectivelyaccelerate heat transfer.

In an embodiment, the system further comprises a circulatory fluid flowsystem that is configured to store thermal energy, wherein the one ormore fluid flow paths are in fluid communication with a fluid flow pathof the circulatory fluid flow system. In another embodiment, thecirculatory fluid flow system comprises a thermal energy storage medium.In another embodiment, the thermal energy storage medium comprisesmolten salt, gravel, sand, steam or water.

In an embodiment, the negative electrode comprises an alkali or alkalineearth metal. In another embodiment, the alkali or alkaline earth metalis lithium, sodium, potassium, magnesium, calcium or a combinationthereof.

In an embodiment, the positive electrode comprises a Group 12 element.In another embodiment, the Group 12 element is selected from the groupconsisting are zinc, cadmium, and mercury. In another embodiment, thepositive electrode further comprises one or more of tin, lead, bismuth,antimony, tellurium, and selenium. In another embodiment, the positiveelectrode comprises one or more of tin, lead, bismuth, antimony,tellurium, and selenium.

In an embodiment, the electrolyte comprises a salt of an alkali oralkaline earth metal. In another embodiment, the system furthercomprises a thermal insulation package that comprises one or more layersof insulating material. In another embodiment, the system furthercomprises a pass-through configured and adapted to facilitate aconnection between hot and cold zones of the energy storage system. Inanother embodiment, the system further comprises at least one wire thatpasses through the pass-through in a circuitous path, wherein a lengthof the wire is at least two times a length of the pass-through. Inanother embodiment, connection comprises a wire, a sensor, a cellcurrent connection, or a cell voltage connection.

In another aspect of the present disclosure, a method for operating anenergy storage system comprises (a) providing an energy storage systemcomprising a plurality of electrochemical cells supported by a framestructure, an individual cell of the plurality of electrochemical cellscomprising a negative electrode, electrolyte and positive electrode,wherein at least one, two, or all of the negative electrode, theelectrolyte and the positive electrode is in a liquid state at anoperating temperature of the individual electrochemical cell, whereinthe frame structure comprises one or more fluid flow paths for bringinga thermal management fluid in thermal communication with at least asubset of the plurality of electrochemical cells; and (b) directing thethermal management fluid through the one or more fluid flow paths.

In an embodiment, the thermal management fluid is directed through theone or more fluid flow paths to maintain a temperature of the individualcell, or cell parts, at the operating temperature. In anotherembodiment, upon directing the thermal management fluid through the oneor more fluid flow paths, the temperature of the individual cell ismaintained to within about +/−60° C. In another embodiment, upondirecting the thermal management fluid through the one or more fluidflow paths, the temperature of the individual cell fluctuates by at mostabout +/−60° C. in a time period of 10 hours, 9 hours, 8 hours, 7 hours,6 hours, 5 hours, 4 hours, 3 hours, 2 hours, 1 hour or less.

In an embodiment, the directing of the thermal management fluid isperformed to maximize the efficiency and/or operating lifetime of theenergy storage system. In another embodiment, the thermal managementfluid is directed at a rate that is varied over time. In anotherembodiment, the thermal management fluid is directed at a rate thatdepends on at least one of (i) a temperature of the energy storagesystem or electrochemical cell thereof; (ii) a rate of change of thetemperature of the energy storage system or electrochemical cellthereof; (iii) whether the energy storage system is charging,discharging or idle; (iv) an anticipated future operation of the energystorage system; and (v) a current or anticipated market condition. Inanother embodiment, the thermal management fluid is directed at a ratethat depends on at least one, two, three, four, or at least all of(i)-(v). In another embodiment, an anticipated future operation of theenergy storage system comprises the time and extent of future charging,discharging and/or idle operation of the energy storage system. Inanother embodiment, a current or anticipated market conditions comprisethe price of energy.

In an embodiment, the thermal management fluid is directed through theone or more fluid flow paths with the aid of a fluid flow system influid communication with the one or more fluid flow paths. In anotherembodiment, the fluid flow system comprises a fan, pump orconvection-assisted flow.

In an embodiment, directing the thermal management fluid through the oneor more fluid flow paths dissipates or adds thermal energy from theplurality of electrochemical cells at a rate of at least about 1 Watt(W). In another embodiment, directing the thermal management fluidthrough the one or more fluid flow paths dissipates thermal energy fromor adds thermal energy to the plurality of electrochemical cells at arate of at most about 100 kilo-Watts (kW).

In an embodiment, the method further comprises rapidly cooling at leasta portion of the energy storage system in response to a potentiallyhazardous event. In another embodiment, the potentially hazardous eventis an earthquake or a cell breach. In another embodiment, upon rapidlycooling, a temperature of a hottest of the plurality of electrochemicalcells decreases from its operating temperature to a temperature below afreezing point of the electrolyte in less than about 4 hours.

In an embodiment, directing the thermal management fluid through the oneor more fluid flow paths comprises directing the thermal managementfluid through a plurality of fluid flow paths. In another embodiment,the thermal management fluid is directed using forced and/or naturalconvection. In another embodiment, flow of the thermal management fluidis directed using natural convection and is controlled by an actuatorthat opens a given fluid flow path of the one or more fluid flow paths.

Another aspect of the present disclosure provides a system comprisingone or more computer processors and memory coupled thereto. The memorycomprises a computer-readable medium with machine executable code that,upon execution by the one or more computer processors, implements any ofthe methods above or elsewhere herein.

In some embodiments, a control system for regulating an energy storagesystem comprises (a) at least one computer processor; and (b) memoryoperatively coupled to the computer processor, the memory comprisingmachine executable code that upon execution by the computer processorimplements a method, the method comprising directing thermal managementfluid through one or more fluid flow paths in a frame structure thatsupports an energy storage system, wherein the fluid flow paths bringthe thermal management fluid in thermal communication with at least asubset of a plurality of electrochemical cells of the energy storagesystem, wherein an individual cell of the plurality of electrochemicalcells comprises a negative electrode, electrolyte and positiveelectrode, and wherein at least two of the negative electrode, theelectrolyte and the positive electrode is in a liquid state at anoperating temperature of the individual electrochemical cell.

In an embodiment, the computer processor and the memory are locatedoutside of a hot zone of the energy storage system. In anotherembodiment, the energy storage system further comprises a temperaturesensor in the hot zone or in thermal communication with the hot zone. Inanother embodiment, the temperature sensor is in electroniccommunication with the computer processor.

In some embodiments, a computer system programmed to direct a thermalmanagement fluid through one or more fluid flow paths of an energystorage system is provided. The energy storage system comprises aplurality of electrochemical cells supported by a frame structure, anindividual cell of the plurality of electrochemical cells comprising anegative electrode, electrolyte and positive electrode, wherein at leastone, two, or all of the negative electrode, the electrolyte and thepositive electrode is in a liquid state at an operating temperature ofthe individual electrochemical cell, wherein the frame structurecomprises the one or more fluid flow paths for bringing the thermalmanagement fluid in thermal communication with at least a subset of theplurality of electrochemical cells.

In an embodiment, the directing of the thermal management fluid isperformed to maintain a temperature of the individual cell, or cellparts, at the operating temperature. In another embodiment, thedirecting of the thermal management fluid is performed to maximize theefficiency and/or operating lifetime of the energy storage system. Inanother embodiment, the thermal management fluid is directed at a ratethat is varied over time.

In an embodiment, the thermal management fluid is directed at a ratethat depends on at least one of (i) a temperature of the energy storagesystem or electrochemical cell thereof; (ii) a rate of change of thetemperature of the energy storage system or electrochemical cellthereof; (iii) whether the energy storage system is charging,discharging or idle; (iv) an expected (or anticipated) future operationof the energy storage system; and (v) a current or anticipated marketcondition. In another embodiment, the thermal management fluid isdirected at a rate that depends on at least one, two, three, four, or atleast all of (i)-(v). In another embodiment, the anticipated futureoperation of the energy storage system comprises the time and extent offuture charging, discharging and/or idle operation of the energy storagesystem. In another embodiment, the current or anticipated marketconditions comprise the price of energy.

Another aspect of the present disclosure provides a computer-readablemedium comprising machine executable code that, upon execution by one ormore computer processors, implements any of the methods above orelsewhere herein.

In some embodiments, a computer readable medium is provided thatcomprises machine-executable code that upon execution by one or morecomputer processors implements a method, the method comprising directingthermal management fluid through one or more fluid flow paths in a framestructure that supports an energy storage system, wherein the fluid flowpaths bring the thermal management fluid in thermal communication withat least a subset of a plurality of electrochemical cells of the energystorage system, wherein an individual cell of the plurality ofelectrochemical cells comprises a negative electrode, electrolyte andpositive electrode, and wherein at least two of the negative electrode,the electrolyte and the positive electrode is in a liquid state at anoperating temperature of the individual electrochemical cell.

In an embodiment, the thermal management fluid is directed through theone or more fluid flow paths to maintain a temperature of the individualcell, or cell parts, at the operating temperature. In anotherembodiment, the thermal management fluid is directed through the one ormore fluid flow paths to maximize the efficiency and/or operatinglifetime of the energy storage system. In another embodiment, thethermal management fluid is directed through the one or more fluid flowpaths at a rate that is varied over time. In another embodiment, thethermal management fluid is directed through the one or more fluid flowpaths at a rate that depends on at least one, two, three, four, or atleast all of (i) a temperature of the energy storage system orelectrochemical cell thereof; (ii) a rate of change of the temperatureof the energy storage system or electrochemical cell thereof; (iii)whether the energy storage system is charging, discharging or idle; (iv)an anticipated future operation of the energy storage system; and (v) acurrent or anticipated market condition. In another embodiment, theanticipated future operation of the energy storage system comprises thetime and extent of future charging, discharging and/or idle operation ofthe energy storage system. In another embodiment, the current oranticipated market conditions comprise the price of energy.

Another aspect of the present disclosure provides an electrochemicalenergy storage device comprising a container including a negativeelectrode, a positive electrode and an electrolyte disposed between thenegative electrode and positive electrode. The electrochemical energystorage device can have a first potential difference between thenegative electrode and positive electrode at a first temperature that isless than about 50° C. and a second potential difference between thenegative electrode and positive electrode at a second temperature of atleast about 250° C. The second potential difference can be greater thanthe first potential difference. At least two of the positive electrode,electrolyte and negative electrode can be liquid at the secondtemperature. The container can have a surface area-to-volume ratio ofless than or equal to about 100 m⁻¹, and the electrochemical energystorage device can maintain at least about 90% of its energy storagecapacity after 500 charge/discharge cycles.

In some embodiments, the container can contain one or moreelectrochemical cells, and an individual electrochemical cell of the oneor more electrochemical cells can include the negative electrode, thepositive electrode and the electrolyte. In some embodiments, over thecharge/discharge cycle, a rate of heat generation in the individualelectrochemical cell can be greater than or equal to about 50% of a rateof heat loss from the individual electrochemical cell. In someembodiments, the electrochemical energy storage device can maintain atleast about 90% of its energy storage capacity after 1,000charge/discharge cycles.

Another aspect of the present disclosure provides an energy storagesystem, comprising a container comprising one or more energy storagecells. An individual energy storage cell of the one or more energystorage cells can comprise at least one liquid electrode and a controlsystem. The control system can comprise a computer processor that isprogrammed to monitor at least one operating temperature of the one ormore energy storage cells and/or the container. The computer processorcan regulate a flow of electrical energy into at least a subset of theone or more energy storage cells such that the subset undergoessustained self-heating over a charge/discharge cycle.

In some embodiments, over the charge/discharge cycle, a rate of heatgeneration in the individual energy storage cell can be greater than orabout equal to a rate of heat loss from the individual energy storagecell. In some embodiments, over the charge/discharge cycle, a rate ofheat generation in the individual energy storage cell can be less thanor equal to about 150% of a rate of heat loss from the individual energystorage cell.

In some embodiments, the computer processor can monitor the at least oneoperating temperature and regulates the flow of electrical energy suchthat the at least one operating temperature is greater than or equal toabout 250° C. and the at least one liquid electrode is maintained as aliquid. In some embodiments, the computer processor can monitor the atleast one operating temperature and regulate the flow of electricalenergy such that over the charge/discharge cycle, the at least oneoperating temperature is greater than or equal to about 250° C.

In some embodiments, the at least one liquid electrode can comprise (i)lithium, sodium, potassium, magnesium, calcium, or any combinationthereof, or (ii) antimony, lead, tin, tellurium, bismuth, or anycombination thereof.

In some embodiments, the individual energy storage cell can furthercomprise an electrolyte adjacent to the at least one liquid electrode.The electrolyte can be a liquid, solid or a paste.

In some embodiments, the one or more energy storage cells can maintainat least about 90% of their energy storage capacity after 100charge/discharge cycles. In some embodiments, the one or more energystorage cells can maintain at least about 90% of their energy storagecapacity after 500 charge/discharge cycles.

In some embodiments, the individual energy storage cell can have anefficiency of at least about 80%. In some embodiments, the individualenergy storage cell can have an efficiency of at least about 80% at acurrent density of at least about 100 mA/cm². In some embodiments, theindividual energy storage cell can have an efficiency of at least about90%. In some embodiments, the individual energy storage cell can have anefficiency of at least about 90% at a current density of at least about100 mA/cm².

In another aspect, the present disclosure provides an energy storagedevice comprising a negative electrode, a positive electrode and anelectrolyte disposed between the negative electrode and positiveelectrode. At least one of the positive electrode and negative electrodecan be liquid at an operating temperature of the energy storage devicethat is greater than a non-operating temperature of the energy storagedevice. The energy storage device can maintain at least about 90% of itsenergy storage capacity after 500 charge/discharge cycles, and theenergy storage device can have an efficiency of at least about 80% at acurrent density of at least about 100 mA/cm².

In some embodiments, the energy storage device can maintain at leastabout 95% of its energy storage capacity after 500 charge/dischargecycles.

Additional aspects and advantages of the present disclosure will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein only illustrative embodiments of thepresent disclosure are shown and described. As will be realized, thepresent disclosure is capable of other and different embodiments, andits several details are capable of modifications in various obviousrespects, all without departing from the disclosure. Accordingly, thedrawings and description are to be regarded as illustrative in nature,and not as restrictive.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings (also “Figure,” “FIG.,” “Figures,” or “FIGs.”herein), of which:

FIG. 1 is an illustration of an electrochemical cell (A) and acompilation (i.e., battery) of electrochemical cells (B and C);

FIG. 2 is a schematic cross sectional illustration of a battery housinghaving a conductor in electrical communication with a current collectorpass through an aperture in the housing;

FIG. 3 is a cross-sectional side view of an electrochemical cell orbattery;

FIG. 4 is a cross-sectional side view of an electrochemical cell orbattery with an intermetallic layer;

FIG. 5 shows an example of a cell pack;

FIG. 6 shows an example of braze connection between the top of aconductive feed-through and the bottom of a cell;

FIG. 7 shows an example of a stack of cell packs, also referred to as acore;

FIG. 8 shows an example of thermal management fluid flowing through aframe;

FIG. 9 shows an example of an insulation insert for central box tubing;

FIG. 10 shows an example of a core of electrochemical cells with ductsfor thermal management fluid;

FIG. 11 shows an example of a computer system of the disclosure;

FIG. 12 is an example of a thermal insulation structure portioncomprising multiple insulation layers and a pass-through;

FIG. 13A is an example of a pass-through with an end cap; and

FIG. 13B shows the pass-through in FIG. 13A with a wire;

FIG. 14 is a cross-sectional side view of an electrochemical cell orbattery with a pressure relief structure.

DETAILED DESCRIPTION

While various embodiments of the invention have been shown and describedherein, it will be obvious to those skilled in the art that suchembodiments are provided by way of example only. Numerous variations,changes, and substitutions may occur to those skilled in the art withoutdeparting from the invention. It should be understood that variousalternatives to the embodiments of the invention described herein may beemployed.

The term “cell,” as used herein, generally refers to an electrochemicalcell. A cell can include a negative electrode of material ‘A’ and apositive electrode of material ‘B’, denoted as A∥B. The positive andnegative electrodes can be separated by an electrolyte. A cell can alsoinclude a housing, one or more current collectors, and a hightemperature electrically isolating seal. In some cases, a cell can beabout 4 inches wide, about 4 inches deep and about 2.5 inches tall. Insome cases, a cell can be about 8 inches wide, about 8 inches deep andabout 2.5 inches tall. In some examples, any given dimension (e.g.,height, width or depth) of an electrochemical cell can be at least about1, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10,12, 14, 16, 18 or 20 inches. In an example, a cell (e.g., each cell) canhave dimensions of about 4 inches×4 inches×2.5 inches. In anotherexample, a cell (e.g., each cell) can have dimensions of about 8inches×8 inches×2.5 inches. In some cases, a cell may have about atleast about 70 Watt-hours of energy storage capacity. In some cases, acell may have at least about 300 Watt-hours of energy storage capacity.

The term “module,” as used herein, generally refers to cells that areattached together in parallel by, for example, mechanically connectingthe cell housing of one cell with the cell housing of an adjacent cell(e.g., cells that are connected together in an approximately horizontalpacking plane). In some cases, the cells are connected to each other byjoining features that are part of and/or connected to the cell body(e.g., tabs protruding from the main portion of the cell body). A modulecan include a plurality of cells in parallel. A module can comprise anynumber of cells, e.g., at least about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 20, or more cells. In some cases, amodule comprises at least about 4, 9, 12, or 16 cells. In some cases, amodule is capable of storing about 700 Watt-hours of energy and/ordelivering at least about 175 Watts (W) of power. In some cases, amodule is capable of storing at least about 1080 Watt-hours of energyand/or delivering at least about 500 Watts of power. In some cases, amodule is capable of storing at least about 1080 Watt-hours of energyand/or delivering at least about 200 Watts (e.g., about 500 Watts) ofpower. In some cases, a module can include a single cell.

The term “pack,” as used herein, generally refers to modules that areattached through different electrical connections (e.g., vertically). Apack can comprise any number of modules, e.g., at least about 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or moremodules. In some cases, a pack comprises at least about 3 modules. Insome cases, a pack is capable of storing at least about 2kilo-Watt-hours of energy and/or delivering at least about 0.4kilo-Watts (e.g., at least about 0.5 kilo-Watts or 1.0 kilo-Watts) ofpower. In some cases, a pack is capable of storing at least about 3kilo-Watt-hours of energy and/or delivering at least about 0.75kilo-Watts (kW) (e.g., at least about 1.5 kilo-Watts) of power. In somecases, a pack comprises at least about 6 modules. In some cases, a packis capable of storing about 6 kilo-Watt-hours of energy and/ordelivering at least about 1.5 kilo-Watts (e.g., about 3 kilo-Watts) ofpower.

The term “core,” as used herein generally refers to a plurality ofmodules or packs that are attached through different electricalconnections (e.g., in series and/or parallel). A core can comprise anynumber of modules or packs, e.g., at least about 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 45, 50, or morepacks. In some cases, the core also comprises mechanical, electrical,and thermal systems that allow the core to efficiently store and returnelectrical energy in a controlled manner. In some cases, a corecomprises at least about 12 packs. In some cases, a core is capable ofstoring at least about 35 kilo-Watt-hours of energy and/or delivering atleast about 7 kilo-Watts of power. In some cases, a core is capable ofstoring at least about 25 kilo-Watt-hours of energy and/or delivering atleast about 6.25 kilo-Watts of power. In some cases, a core comprises atleast about 36 packs. In some cases, a core is capable of storing atleast about 200 kilo-Watt-hours of energy and/or delivering at leastabout 40, 50, 60, 70, 80, 90 or 100 kilo-Watts or more of power.

The term “core enclosure”, or “CE,” as used herein, generally refers toa plurality of cores that are attached through different electricalconnections (e.g., in series and/or parallel). A CE can comprise anynumber of cores, e.g., at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 20, or more cores. In some cases, the CEcontains cores that are connected in parallel with appropriate by-passelectronic circuitry, thus enabling a core to be disconnected whilecontinuing to allow the other cores to store and return energy. In somecases, a CE comprises at least 4 cores. In some cases, a CE is capableof storing at least about 100 kilo-Watt-hours of energy and/ordelivering about 25 kilo-Watts of power. In some cases, a CE comprises 4cores. In some cases, a CE is capable of storing about 100kilo-Watt-hours of energy and/or delivering about 25 kilo-Watts ofpower. In some cases, a CE is capable of storing about 400kilo-Watt-hours of energy and/or delivering at least about 80kilo-Watts, e.g., at least or about 80, 100, 120, 140, 160, 180 or 200kilo-Watts or more of power.

The term “system,” as used herein, generally refers to a plurality ofcores or CEs that are attached through different electrical connections(e.g., in series and/or parallel). A system can comprise any number ofcores or CEs, e.g., at least about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, or more cores. In some cases, a systemcomprises 20 CEs. In some cases, a system is capable of storing about 2mega-Watt-hours of energy and/or delivering at least about 400kilo-Watts (e.g., about 500 kilo-Watts or about 1000 kilo-Watts) ofpower. In some cases, a system comprises 5 CEs. In some cases, a systemis capable of storing about 2 mega-Watt-hours of energy and/ordelivering at least about 400 kilo-Watts, e.g., at least about 400, 500,600, 700, 800, 900, 1000 kilo-Watts or more of power.

A group of cells (e.g., a core, a CE, a system, etc.) with a givenenergy capacity and power capacity (e.g., a CE or a system capable ofstoring a given amount of energy) may be configured to deliver at leastabout 10%, at least about 20%, at least about 30%, at least about 40%,at least about 50%, at least about 60%, at least about 70%, at leastabout 80%, at least about 90%, at least about 95%, or about 100% of agiven (e.g., rated) power level. For example, a 1000 kW system may becapable of also operating at 500 kW, but a 500 kW system may not be ableto operate at 1000 kW. In some cases, a system with a given energycapacity and power capacity (e.g., a CE or a system capable of storing agiven amount of energy) may be configured to deliver less than about100%, less than about 110%, less than about 125%, less than about 150%,less than about 175%, or less than about 200% of a given (e.g., rated)power level, and the like. For example, the system may be configured toprovide more than its rated power capacity for a period of time that isless than the time it may take to consume its energy capacity at thepower level that is being provided (e.g., provide power that is greaterthan the rated power of the system for a period of time corresponding toless than about 1%, less than about 10% or less than about 50% of itsrated energy capacity).

The term “battery,” as used herein, generally refers to one or moreelectrochemical cells connected in series and/or parallel. A battery cancomprise any number of electrochemical cells, modules, packs, cores, CEsor systems. A battery may undergo at least one charge/discharge ordischarge/charge cycle (“cycle”).

The term “vertical,” as used herein, generally refers to a directionthat is parallel to the gravitational acceleration vector (g).

The term “charge cutoff voltage” or “CCV,” as used herein, generallyrefers to the voltage at which a cell is fully or substantially fullycharged, such as a voltage cutoff limit used in a battery when cycled ina constant current mode.

The term “open circuit voltage” or “OCV,” as used herein, generallyrefers to the voltage of a cell (e.g., fully or partially charged) whenit is disconnected from any circuit or external load (i.e., when nocurrent is flowing through the cell).

The term “voltage” or “cell voltage,” as used herein, generally refersto the voltage of a cell (e.g., at any state of charge orcharging/discharging condition). In some cases, voltage or cell voltagemay be the open circuit voltage. In some cases, the voltage or cellvoltage can be the voltage during charging or during discharging.

Voltages of the present disclosure may be taken or represented withrespect to reference voltages, such as ground (0 volt (V)), or thevoltage of the opposite electrode in an electrochemical cell.

Electrochemical Cells, Devices and Systems

The present disclosure provides electrochemical energy storage devices(e.g., batteries) and systems. An electrochemical energy storage devicegenerally includes at least one electrochemical cell, also “cell” and“battery cell” herein, sealed (e.g., hermetically sealed) within ahousing. A cell can be configured to deliver electrical energy (e.g.,electrons under potential) to a load, such as, for example, anelectronic device, another energy storage device or a power grid.

An electrochemical cell of the disclosure can include a negativeelectrode, an electrolyte adjacent to the negative electrode, and apositive electrode adjacent to the electrolyte. The negative electrodecan be separated from the positive electrode by the electrolyte. Thenegative electrode can be an anode during discharge. The positiveelectrode can be a cathode during discharge.

In some examples, an electrochemical cell is a liquid metal batterycell. In some examples, a liquid metal battery cell can include a liquidelectrolyte arranged between a negative liquid (e.g., molten) metalelectrode and a positive liquid (e.g., molten) metal, metalloid and/ornon-metal electrode. In some cases, a liquid metal battery cell has amolten alkaline earth metal (e.g., magnesium, calcium) or alkali metal(e.g., lithium, sodium, potassium) negative electrode, an electrolyte,and a molten metal positive electrode. The molten metal positiveelectrode can include, for example, one or more of tin, lead, bismuth,antimony, tellurium and selenium. For example, the positive electrodecan include Pb or a Pb—Sb alloy. The positive electrode can also includeone or more transition metals or d-block elements (e.g., Zn, Cd, Hg)alone or in combination with other metals, metalloids or non-metals,such as, for example, a Zn—Sn alloy or Cd—Sn alloy. In some examples,the positive electrode can comprise a metal or metalloid that has onlyone stable oxidation state (e.g., a metal with a single or singularoxidation state). Any description of a metal or molten metal positiveelectrode, or a positive electrode, herein may refer to an electrodeincluding one or more of a metal, a metalloid and a non-metal. Thepositive electrode may contain one or more of the listed examples ofmaterials. In an example, the molten metal positive electrode caninclude lead and antimony. In some examples, the molten metal positiveelectrode may include an alkali or alkaline earth metal alloyed in thepositive electrode.

In some examples, an electrochemical energy storage device includes aliquid metal negative electrode, a liquid metal positive electrode, anda liquid salt electrolyte separating the liquid metal negative electrodeand the liquid metal positive electrode. The negative electrode caninclude an alkali or alkaline earth metal, such as lithium, sodium,potassium, rubidium, cesium, magnesium, barium, calcium, sodium, orcombinations thereof. The positive electrode can include elementsselected from transition metals or d-block elements (e.g., Group 12),Group IIIA, IVA, VA and VIA of the periodic table of the elements, suchas zinc, cadmium, mercury, aluminum, gallium, indium, silicon,germanium, tin, lead, pnicogens (e.g., arsenic, bismuth and antimony),chalcogens (e.g., sulfur, tellurium and selenium), or combinationsthereof. In some examples, the positive electrode comprises a Group 12element of the periodic table of the elements, such as one or more ofzinc (Zn), cadmium (Cd) and mercury (Hg). In some cases, the positiveelectrode may form a eutectic or off-eutectic mixture (e.g., enablinglower operating temperature of the cell in some cases). In someexamples, the positive electrode comprises a first positive electrodespecies and a second positive electrode species at a ratio (mol-%) ofabout 20:80, 40:60, 50:50, or 80:20 of the first positive electrodespecies to the second electrode species. In some examples, the positiveelectrode comprises Sb and Pb at a ratio (mol-%) of about 20:80, 40:60,50:50, or 80:20 Sb to Pb. In some examples, the positive electrodecomprises between about 20 mol % and 80 mol-% of a first positiveelectrode species mixed with a second positive electrode species. Insome cases, the positive electrode comprises between about 20 mol-% and80 mol-% Sb (e.g., mixed with Pb). In some cases, the positive electrodecomprises between about 20 mol-% and 80 mol-% Pb (e.g., mixed with Sb).In some examples, the positive electrode comprises one or more of Zn,Cd, Hg, or such material(s) in combination with other metals, metalloidsor non-metals, such as, for example, a Zn—Sn alloy, Zn—Sn alloy, Cd—Snalloy, Zn—Pb alloy, Zn—Sb alloy, or Bi. In an example, the positiveelectrode can comprise 15:85, 50:50, 75:25 or 85:15 mol-% Zn:Sn.

The electrolyte can include a salt (e.g., molten salt), such as analkali or alkaline earth metal salt. The alkali or alkaline earth metalsalt can be a halide, such as a fluoride, chloride, bromide, or iodideof the active alkali or alkaline earth metal, or combinations thereof.In an example, the electrolyte (e.g., in Type 1 or Type 2 chemistries)includes lithium chloride. In some examples, the electrolyte cancomprise sodium fluoride (NaF), sodium chloride (NaCl), sodium bromide(NaBr), sodium iodide (NaI), lithium fluoride (LiF), lithium chloride(LiCl), lithium bromide (LiBr), lithium iodide (LiI), potassium fluoride(KF), potassium chloride (KCl), potassium bromide (KBr), potassiumiodide (KI), calcium fluoride (CaF₂), calcium chloride (CaCl₂)), calciumbromide (CaBr₂), calcium iodide (CaI₂), or any combination thereof. Inanother example, the electrolyte includes magnesium chloride (MgCl₂). Asan alternative, the salt of the active alkali metal can be, for example,a non-chloride halide, carbonate, hydroxide, nitrate, nitrite, sulfate,sulfite, or combinations thereof. In some cases, the electrolyte cancomprise a mixture of salts (e.g., 25:55:20 mol-% LiF:LiCl:LiBr,50:37:14 mol-% LiCl:LiF:LiBr, etc.). The electrolyte may exhibit low(e.g., minimal) electronic conductance (e.g., electronic shorting mayoccur through the electrolyte via valence reactions of PbCl₂↔PbCl₃ whichincreases electronic conductance). For example, the electrolyte can havean electronic transference number (i.e., percentage of electrical(electronic and ionic) charge that is due to the transfer of electrons)of less than or equal to about 0.03% or 0.3%.

In some cases, the negative electrode and the positive electrode of anelectrochemical energy storage device are in the liquid state at anoperating temperature of the energy storage device. To maintain theelectrodes in the liquid states, the battery cell may be heated to anysuitable temperature. In some examples, the battery cell is heated toand/or maintained at a temperature of about 100° C., about 150° C.,about 200° C., about 250° C., about 300° C., about 350° C., about 400°C., about 450° C., about 500° C., about 550° C., about 600° C., about650° C., or about 700° C. The battery cell may be heated to and/ormaintained at a temperature of at least about 100° C., at least about150° C., at least about 200° C., at least about 250° C., at least about300° C., at least about 350° C., at least about 400° C., at least about450° C., at least about 500° C., at least about 550° C., at least about600° C., at least about 650° C., at least about 700° C., at least about800° C., or at least about 900° C. In such a case, the negativeelectrode, electrolyte and positive electrode can be in a liquid (ormolten) state. In some situations, the battery cell is heated to betweenabout 200° C. and about 600° C., between about 500° C. and about 550°C., or between about 450° C. and about 575° C.

In some implementations, the electrochemical cell or energy storagedevice may be at least partially or fully self-heated. For example, abattery may be sufficiently insulated, charged, discharged and/orconditioned at sufficient rates, and/or cycled a sufficient percentageof the time to allow the system to generate sufficient heat throughinefficiencies of the cycling operation that cells are maintained at agiven operating temperature (e.g., a cell operating temperature abovethe freezing point of at least one of the liquid components) without theneed for additional energy to be supplied to the system to maintain theoperating temperature.

Electrochemical cells of the disclosure may be adapted to cycle betweencharged (or energy storage) modes and discharged modes. In someexamples, an electrochemical cell can be fully charged, partiallycharged or partially discharged, or fully discharged.

In some implementations, during a charging mode of an electrochemicalenergy storage device, electrical current received from an externalpower source (e.g., a generator or an electrical grid) may cause metalatoms in the metal positive electrode to release one or more electrons,dissolving into the electrolyte as a positively charged ion (i.e.,cation). Simultaneously, cations of the same species can migrate throughthe electrolyte and may accept electrons at the negative electrode,causing the cations to transition to a neutral metal species, therebyadding to the mass of the negative electrode. The removal of the activemetal species from the positive electrode and the addition of the activemetal to the negative electrode stores electrochemical energy. In somecases, the removal of a metal from the positive electrode and theaddition of its cation to the electrolyte can store electrochemicalenergy. In some cases, electrochemical energy can be stored through acombination of removal of the active metal species from the positiveelectrode and its addition to the negative electrode, and the removal ofone or more metals (e.g., different metals) from the positive electrodeand their addition to the electrolyte (e.g., as cations). During anenergy discharge mode, an electrical load is coupled to the electrodesand the previously added metal species in the negative electrode can bereleased from the metal negative electrode, pass through the electrolyteas ions, and deposit as a neutral species in the positive electrode (andin some cases alloy with the positive electrode material), with the flowof ions accompanied by the external and matching flow of electronsthrough the external circuit/load. In some cases, one or more cations ofpositive electrode material previously released into the electrolyte candeposit as neutral species in the positive electrode (and in some casesalloy with the positive electrode material), with the flow of ionsaccompanied by the external and matching flow of electrons through theexternal circuit/load. This electrochemically facilitated metal alloyingreaction discharges the previously stored electrochemical energy to theelectrical load.

In a charged state, the negative electrode can include negativeelectrode material and the positive electrode can include positiveelectrode material. During discharging (e.g., when the battery iscoupled to a load), the negative electrode material yields one or moreelectrons, and cations of the negative electrode material. In someimplementations, the cations migrate through the electrolyte to thepositive electrode material and react with the positive electrodematerial (e.g., to form an alloy). In some implementations, ions of thepositive metal species (e.g., cations of the positive electrodematerial) accept electrons at the positive electrode and deposit as ametal on the positive electrode. During charging, in someimplementations, the alloy at the positive electrode disassociates toyield cations of the negative electrode material, which migrate throughthe electrolyte to the negative electrode. In some implementations, oneor more metal species at the positive electrode disassociates to yieldcations of the negative electrode material in the electrolyte. In someexamples, ions can migrate through an electrolyte from an anode to acathode, or vice versa. In some cases, ions can migrate through anelectrolyte in a push-pop fashion in which an entering ion of one typeejects an ion of the same type from the electrolyte. For example, duringdischarge, an alkali metal anode and an alkali metal chlorideelectrolyte can contribute an alkali metal cation to a cathode by aprocess in which an alkali metal cation formed at the anode interactswith the electrolyte to eject an alkali metal cation from theelectrolyte into the cathode. The alkali metal cation formed at theanode in such a case may not necessarily migrate through the electrolyteto the cathode. The cation can be formed at an interface between theanode and the electrolyte, and accepted at an interface of the cathodeand the electrolyte.

The present disclosure provides Type 1 and Type 2 cells, which can varybased on, and be defined by, the composition of the active components(e.g., negative electrode, electrolyte and positive electrode), andbased on the mode of operation of the cells (e.g., low voltage modeversus high voltage mode). A cell can comprise materials that areconfigured for use in Type 2 mode of operation. A cell can comprisematerials that are configured for use in Type 1 mode of operation. Insome cases, a cell can be operated in both a high voltage (Type 2)operating mode and the low voltage (Type 1) operating mode. For example,a cell with positive and negative electrode materials that areordinarily configured for use in a Type 1 mode can be operated in a Type2 mode of operation. A cell can be cycled between Type 1 and Type 2modes of operation. A cell can be initially charged (or discharged)under Type 1 mode to a given voltage (e.g., 0.5 V to 1 V), andsubsequently charged (then discharged) under Type 2 mode to a highervoltage (e.g., 1.5 V to 2.5 V, or 1.5 V to 3 V). In some cases, cellsoperated under Type 2 mode can operate at a voltage between electrodesthat can exceed those of cells operated under Type 1 mode. In somecases, Type 2 cell chemistries can operate at a voltage betweenelectrodes that can exceed those of Type 1 cell chemistries operatedunder Type 1 mode. Type 2 cells can be operated in Type 2 mode.

In an example Type 1 cell, upon discharging, cations formed at thenegative electrode can migrate into the electrolyte. Concurrently, theelectrolyte can provide a cation of the same species (e.g., the cationof the negative electrode material) to the positive electrode, which canreduce from a cation to a neutrally charged metallic species, and alloywith the positive electrode. In a discharged state, the negativeelectrode can be depleted (e.g., partially or fully) of the negativeelectrode material (e.g., Li, Na, K, Mg, Ca). During charging, the alloyat the positive electrode can disassociate to yield cations of thenegative electrode material (e.g., Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, whichmigrates into the electrolyte. The electrolyte can then provide cations(e.g., the cation of the negative electrode material) to the negativeelectrode, where the cations accept one or more electrons from anexternal circuit and are converted back to a neutral metal species,which replenishes the negative electrode to provide a cell in a chargedstate. A Type 1 cell can operate in a push-pop fashion, in which theentry of a cation into the electrolyte results in the discharge of thesame cation from the electrolyte.

In an example Type 2 cell, in a discharged state the electrolytecomprises cations of the negative electrode material (e.g., Li⁺, Na⁺,K⁺, Mg²⁺, Ca²⁺), and the positive electrode comprises positive electrodematerial (e.g., Sb, Pb, Sn, Bi, Zn, Hg). During charging, a cation ofthe negative electrode material from the electrolyte accepts one or moreelectrons (e.g., from a negative current collector) to form the negativeelectrode comprising the negative electrode material. In some examples,the negative electrode material is liquid and wets into a foam (orporous) structure of the negative current collector. In some examples,negative current collector may not comprise foam (or porous) structure.In some examples, the negative current collector may comprise a metal,such as, for example, tungsten (e.g., to avoid corrosion from Zn),tungsten carbide or molybdenum negative collector not comprising Fe—Nifoam. Concurrently, positive electrode material from the positiveelectrode sheds electrons (e.g., to a positive current collector) anddissolves into the electrolyte as cations of the positive electrodematerial (e.g., Sb³⁺, Pb²⁺, Bi³⁺, Zn²⁺, Hg²⁺). The concentration of thecations of the positive electrode material can vary in verticalproximity within the electrolyte (e.g., as a function of distance abovethe positive electrode material) based on the atomic weight anddiffusion dynamics of the cation material in the electrolyte. In someexamples, the cations of the positive electrode material areconcentrated in the electrolyte near the positive electrode.

In some implementations, negative electrode material may not need to beprovided at the time of assembly of a cell that can be operated in aType 2 mode. For example, a Li∥Pb cell or an energy storage devicecomprising such cell(s) can be assembled in a discharged state havingonly a Li salt electrolyte and a Pb or Pb alloy (e.g., Pb—Sb) positiveelectrode (i.e., Li metal may not be required during assembly).

Although electrochemical cells of the present disclosure have beendescribed, in some examples, as operating in a Type 1 mode or Type 2mode, other modes of operation are possible. Type 1 mode and Type 2 modeare provided as examples and are not intended to limit the various modesof operation of electrochemical cells disclosed herein.

In some cases, an electrochemical cell comprises a liquid metal negativeelectrode (e.g., sodium (Na) or lithium (Li)), and a solidion-conducting (e.g., β″-alumina ceramic) electrolyte, and a liquidpositive electrode. Such a cell can be a high temperature battery. Oneor more such cells can be provided in an electrochemical energy storagedevice. The negative electrode can include an alkali or alkaline earthmetal, such as, for example, lithium, sodium, potassium, magnesium,calcium, or combinations thereof. The positive electrode may comprise aliquid chalcogen or molten chalcogenide (e.g., sulfur (S), selenium(Se), or tellurium (Te)), and/or a molten salt comprising a transitionmetal halide (e.g., NiCl₃, FeCl₃) and/or other (e.g., supporting)compounds (e.g., NaCl, NaF, NaBr, NaI, KCl, LiCl, bromide salts), or anycombination thereof. In some instances, the solid ion conductingelectrolyte is a beta alumina (e.g., β″-alumina) ceramic capable ofconducting sodium ions at elevated or high temperature (e.g., aboveabout 200° C., above about 250° C., above about 300° C., or above about350° C.). In some instances, the solid ion-conducting electrolyteoperates above about 100° C., above about 150° C., above about 200° C.,above about 250° C., above about 300° C., or above about 350° C.

Batteries and Housings

Electrochemical cells of the disclosure can include housings that may besuited for various uses and operations. A housing can include one cellor a plurality of cells. A housing can be configured to electricallycouple the electrodes to a switch, which can be connected to theexternal power source and the electrical load. The cell housing mayinclude, for example, an electrically conductive container that iselectrically coupled to a first pole of the switch and/or another cellhousing, and an electrically conductive container lid that iselectrically coupled to a second pole of the switch and/or another cellhousing. The cell can be arranged within a cavity of the container. Afirst one of the electrodes of the cell (e.g., positive electrode) cancontact and be electrically coupled with an endwall of the container. Asecond one of the electrodes of the cell (e.g., negative electrode) cancontact and be electrically coupled with a conductive feed-through orconductor (e.g., negative current lead) on the container lid. Anelectrically insulating seal (e.g., bonded ceramic ring) mayelectrically isolate negative potential portions of the cell frompositive portions of the container (e.g., electrically insulate thenegative current lead from the positive current lead). In an example,the negative current lead and the container lid (e.g., cell cap) can beelectrically isolated from each other, where a dielectric sealantmaterial can be placed between the negative current lead and the cellcap. As an alternative, a housing can include an electrically insulatingsheath (e.g., alumina sheath) or a corrosion-resistant and electricallyconductive sheath or crucible (e.g., graphite sheath or crucible). Insome cases, a housing and/or container may be a battery housing and/orcontainer.

A battery, as used herein, can comprise a plurality of electrochemicalcells. The cell(s) can include housings. Individual cells can beelectrically coupled to one another in series and/or in parallel. Inseries connectivity, the positive terminal of a first cell is connectedto a negative terminal of a second cell. In parallel connectivity, thepositive terminal of a first cell can be connected to a positiveterminal of a second, and/or additional, cell(s). Similarly, cellmodules, packs, cores, CEs and systems can be connected in series and/orin parallel in the same manner as described for cells.

Reference will now be made to the figures, wherein like numerals referto like parts throughout. It will be appreciated that the figures andfeatures therein are not necessarily drawn to scale.

With reference to FIG. 1 , an electrochemical cell (A) is a unitcomprising an anode and a cathode. The cell may comprise an electrolyteand be sealed in a housing as described herein. In some cases, theelectrochemical cells can be stacked (B) to form a battery (i.e., acompilation of one or more electrochemical cells). The cells can bearranged in parallel, in series, or both in parallel and in series (C).Further, cell modules, packs, cores, CEs and/or systems can be connectedin series and/or in parallel. Interconnections 101 may connectindividual cells and/or groups of cells.

The cells can be arranged in groups (e.g., modules, packs, cores, CEs,systems, or any other group comprising one or more electrochemicalcells). In some cases, such groups of electrochemical cells may allow agiven number of cells to be controlled or regulated together at thegroup level (e.g., in concert with or instead of regulation/control ofindividual cells).

The battery may be assembled through repeated addition of individualcells or groups of cells. In one example, cells can be assembled intomodules, which can be stacked to form packs, which can then beinterconnected to form cores. In some cases, the packs may be assembled(e.g., vertically and/or horizontally) on trays, which is anotherexample of a group of electrochemical cells; the trays can be assembled(e.g., vertically and/or horizontally) to form cores. Further, the corescan then be interconnected to form CEs and systems. In another example,cells can be assembled into modules, which can be interconnected (e.g.,vertically and horizontally) to form cores. In yet another example,cells can be stacked to form a single cell tower (see, for example,configuration B in FIG. 1 ), which is yet another example of a group ofelectrochemical cells. Multiple cell towers, each comprising multiplecells stacked vertically on top one another, can then be added togetherto form, for example, a pack. Thus, in an example, a pack comprising astack of 4 modules, each module comprising a 2 by 2 array of cells, canalso be assembled by interconnecting 4 towers with 4 cells each(arranged in a 2 by 2 array of towers). Groups of cells utilized forassembly purposes may or may not be the same as groups of cells utilizedfor regulation/control purposes. Groups of cells may be supported by(e.g., packs or cores) or comprise (e.g., trays or towers) variousframes. The frames of different groups of cells may be connected duringassembly.

As described in greater detail elsewhere herein, individual cells orportion(s) thereof, groups of cells, or devices or systems comprisingsuch cell(s) (e.g., energy storage systems comprising energy storagedevices such as batteries) can be thermally maintained and/or regulated,e.g., by a thermal management system. The thermal management system maybe distributed across various portions of the energy storagedevice/system, and/or across a system for operating the energy storagedevice/system. In some implementations, one or more frames may be usedfor thermal management of the systems herein. Such thermal managementframes may also provide structural support. At least a portion of thethermal management system may be assembled by connecting frames. Theframes may be configured, for example, to form a system of fluid flowpathways and/or ducts comprising a thermal management fluid. In somecases, the frames may be configured to be in thermal contact with (e.g.,via the thermal management fluid) one or more electrochemical cells.

Electrochemical cells of the disclosure (e.g., Type 1 cell operated inType 2 mode, Type 1 cell operated in Type 1 mode, or Type 2 cell) may becapable of storing, receiving input of (“taking in”), discharging,and/or returning a suitably large amount of energy (e.g., substantiallylarge amounts of energy). In some instances, a cell is capable ofstoring, taking in, discharging, and/or returning about 1 Watt-hour(Wh), about 5 Wh, 25 Wh, about 50 Wh, about 100 Wh, about 250 Wh, about500 Wh, about 1 kilo-Watt-hour (kWh), about 1.5 kWh, about 2 kWh, about3 kWh, about 5 kWh, about 10 kWh, about 15 kWh, about 20 kWh, about 30kWh, about 40 kWh, or about 50 kWh. In some instances, the battery iscapable of storing, taking in, discharging, and/or returning at leastabout 1 Wh, at least about 5 Wh, at least about 25 Wh, at least about 50Wh, at least about 100 Wh, at least about 250 Wh, at least about 500 Wh,at least about 1 kWh, at least about 1.5 kWh, at least about 2 kWh, atleast about 3 kWh, at least about 5 kWh, at least about 10 kWh, at leastabout 15 kWh, at least about 20 kWh, at least about 30 kWh, at leastabout 40 kWh, or at least about 50 kWh. It is recognized that the amountof energy stored in an electrochemical cell and/or battery may be lessthan the amount of energy taken into the electrochemical cell and/orbattery (e.g., due to inefficiencies and losses). A cell can have suchenergy storage capacities upon operating at any of the current densitiesherein.

A cell can be capable of providing a current at a current density of atleast about 10 milli-amperes per square centimeter (mA/cm²), 20 mA/cm²,30 mA/cm², 40 mA/cm², 50 mA/cm², 60 mA/cm², 70 mA/cm², 80 mA/cm², 90mA/cm², 100 mA/cm², 200 mA/cm², 300 mA/cm², 400 mA/cm², 500 mA/cm², 600mA/cm², 700 mA/cm², 800 mA/cm², 900 mA/cm², 1 A/cm², 2 A/cm², 3 A/cm², 4A/cm², 5 A/cm², or 10 A/cm², where the current density is determinedbased on the effective cross-sectional area of the electrolyte and wherethe cross-sectional area is the area that is orthogonal to the net flowdirection of ions through the electrolyte during charge or dischargingprocesses. In some instances, a cell can be capable of operating at adirect current (DC) efficiency of at least about 10%, 20%, 30%, 35%,40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 90%, 95% and the like. Insome instances, a cell can be capable of operating at a chargeefficiency (e.g., Coulombic charge efficiency) of at least about 10%,20%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 90%, 95%, 98%, 99%, 99.5%,99.9%, 99.95%, 99.99%, and the like.

In a charged state, electrochemical cells of the disclosure (e.g., Type1 cell operated in Type 2 mode, Type 1 cell operated in Type 1 mode, orType 2 cell) can have (or can operate at) a voltage of at least about0.5 V, 0.6 V, 0.7 V, 0.8 V, 0.9 V, 1.0 V, 1.1 V, 1.2 V, 1.3 V, 1.4 V,1.5 V, 1.6 V, 1.7 V, 1.8 V, 1.9 V, 2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V,2.5 V, 2.6 V, 2.7 V, 2.8 V, 2.9 V, or 3.0 V. In some cases, a cell canhave an open circuit voltage (OCV) of at least about 0.5 V, 0.6 V, 0.7V, 0.8 V, 0.9 V, 1.0 V, 1.1 V, 1.2 V, 1.3 V, 1.4 V, 1.5 V, 1.6 V, 1.7 V,1.8 V, 1.9 V, 2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V, 2.5 V, 2.6 V, 2.7 V,2.8 V, 2.9 V, or 3.0 V. In an example, a cell has an open circuitvoltage greater than about 0.5 V, greater than about 1 V, greater thanabout 2 V, or greater than about 3 V. In some cases, a charge cutoffvoltage (CCV) of a cell is from about 0.5 V to 1.5 V, 1 V to 3 V, 1.5 Vto 2.5 V, 1.5 V to 3 V, or 2 V to 3 V in a charged state. In some cases,a charge cutoff voltage (CCV) of a cell is at least about 0.5 V, 0.6 V,0.7 V, 0.8 V, 0.9 V, 1.0 V, 1.1 V, 1.2 V, 1.3 V, 1.4 V, 1.5 V, 1.6 V,1.7 V, 1.8 V, 1.9 V, 2.0 V, 2.1 V, 2.2 V, 2.3 V, 2.4 V, 2.5 V, 2.6 V,2.7 V, 2.8 V, 2.9 V or 3.0 V. In some cases, a voltage of a cell (e.g.,operating voltage) is between about 0.5 V and 1.5 V, 1 V and 2 V, 1 Vand 2.5 V, 1.5 V and 2.0 V, 1 V and 3 V, 1.5 V and 2.5 V, 1.5 V and 3 V,or 2 V and 3 V in a charged state. A cell can provide such voltage(s)(e.g., voltage, OCV and/or CCV) upon operating at up to and exceedingabout 10 cycles, 20 cycles, 30 cycles, 40 cycles, 50 cycles, 100 cycles,200 cycles, 300 cycles, 400 cycles, 500 cycles, 600 cycles, 700 cycles,800 cycles, 900 cycles, 1,000 cycles, 2,000 cycles, 3,000 cycles, 4,000cycles, 5,000 cycles, 10,000 cycles, 20,000 cycles, 50,000 cycles,100,000 cycles, or 1,000,000 or more cycles (also “charge/dischargecycles” herein). A cell can be operated without a substantial decreasein capacity. During operation at an operating temperature of the cell,the cell can have a negative electrode, electrolyte and positiveelectrode in a liquid (or molten) state.

An electrochemical cell of the present disclosure can have a responsetime of any suitable value (e.g., suitable for responding todisturbances in the power grid). In some instances, the response time isabout 100 milliseconds (ms), about 50 ms, about 10 ms, about 1 ms, andthe like. In some cases, the response time is at most about 100milliseconds (ms), at most about 50 ms, at most about 10 ms, at mostabout 1 ms, and the like.

A compilation or array of cells (e.g., battery) can include any suitablenumber of cells, such as at least about 2, at least about 5, at leastabout 10, at least about 50, at least about 100, at least about 500, atleast about 1000, at least about 5000, at least about 10000, and thelike. In some examples, a battery includes 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600,700, 800, 900, 1,000, 2,000, 5,000, 10,000, 20,000, 50,000, 100,000,500,000, or 1,000,000 cells.

In some implementations, one or more types of cells can be included inenergy storage systems of the present disclosure. For example, an energystorage device can comprise Type 2 cells or a combination of Type 1cells and Type 2 cells (e.g., 50% Type 1 cells and 50% Type 2 cells).Such cells can be operated under Type 2 mode. In some cases, a firstportion of the cells may be operated in Type 1 mode, and a secondportion of the cells may be operated in Type 2 mode.

Batteries of the disclosure may be capable of storing, taking in,discharging, and/or returning a suitably large amount of energy (e.g., asubstantially large amount of energy) for use with a power grid (i.e., agrid-scale battery) or other loads or uses. In some instances, a batteryis capable of storing, taking in, discharging, and/or returning about 5kilo-Watt-hour (kWh), about 25 kWh, about 50 kWh, about 100 kWh, about500 kWh, about 1 mega-Watt-hour (MWh), about 1.5 MWh, about 2 MWh, about3 MWh, about 5 MWh, about 10 MWh, about 25 MWh, about 50 MWh, or about100 MWh. In some instances, the battery is capable of storing, takingin, discharging, and/or returning at least about 1 kWh, at least about 5kWh, at least about 25 kWh, at least about 50 kWh, at least about 100kWh, at least about 500 kWh, at least about 1 MWh, at least about 1.5MWh, at least about 2 MWh, at least about 3 MWh, at least about 4 MWh,at least about 5 MWh, at least about 10 MWh, at least about 25 MWh, atleast about 50 MWh, or at least about 100 MWh.

In some instances, the cells and cell housings are stackable. Anysuitable number of cells can be stacked. Cells can be stackedside-by-side, on top of each other, or both. In some instances, at leastabout 3, 6, 10, 50, 100, or 500 cells are stacked. In some cases, astack of 100 cells is capable of storing, taking in, discharging, and/orreturning at least 50 kWh of energy. A first stack of cells (e.g., 10cells) can be electrically connected to a second stack of cells (e.g.,another 10 cells) to increase the number of cells in electricalcommunication (e.g., 20 in this instance). In some instances, an energystorage device comprises a stack of 1 to 10, 11 to 50, 51 to 100, ormore electrochemical cells.

An electrochemical energy storage device can include one or moreindividual electrochemical cells. An electrochemical cell can be housedin a container, which can include a container lid (e.g., cell cap) andseal component. The device can include at least 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 20, 30, 40, 50, 100, 200, 300, 400, 500, 1000, 10,000, 100,000 or1,000,000 cells. The container lid may utilize, for example, a seal(e.g., annular dielectric gasket) to electrically isolate the containerfrom the container lid. Such a component may be constructed from anelectrically insulating material, such as, for example, glass, oxideceramics, nitride ceramics, chalcogenides, or a combination thereof(e.g., ceramic, silicon oxide, aluminum oxide, nitrides comprising boronnitride, aluminum nitride, zirconium nitride, titanium nitride, carbidescomprising silicon carbide, titanium carbide, or other oxides comprisingof lithium oxide, calcium oxide, barium oxide, yttrium oxide, siliconoxide, aluminum oxide, or lithium nitride, lanthanum oxide, or anycombinations thereof). The seal may be made hermetic by one or moremethods. For example, the seal may be subject to relatively highcompressive forces (e.g., greater than about 1,000 psi or greater thanabout 10,000 psi) between the container lid and the container in orderto provide a seal in addition to electrical isolation. Alternatively,the seal may be bonded through a weld, a braze, or other chemicallyadhesive material that joins relevant cell components to the insulatingsealant material.

FIG. 2 schematically illustrates a battery that comprises anelectrically conductive housing 201 and a conductor 202 in electricalcommunication with a current collector 203. The battery of FIG. 2 can bea cell of an energy storage device. The conductor can be electricallyisolated from the housing and can protrude through the housing throughan aperture in the housing such that the conductor of a first cell is inelectrical communication with the housing of a second cell when thefirst and second cells are stacked.

In some cases, a cell comprises a negative current collector, a negativeelectrode, an electrolyte, a positive electrode and a positive currentcollector. The negative electrode can be part of the negative currentcollector. As an alternative, the negative electrode is separate from,but otherwise kept in electrical communication with, the negativecurrent collector. The positive electrode can be part of the positivecurrent collector. As an alternative, the positive electrode can beseparate from, but otherwise kept in electrical communication with, thepositive current collector.

A cell housing can comprise an electrically conductive container and aconductor in electrical communication with a current collector. Theconductor may protrude through the housing through an aperture in thecontainer and may be electrically isolated from the container. Theconductor of a first housing may contact the container of a secondhousing when the first and second housings are stacked.

In some instances, the area of the aperture through which the conductorprotrudes from the housing and/or container is small relative to thearea of the housing and/or container. In some cases, the ratio of thearea of the aperture to the area of the housing is about 0.001, about0.005, about 0.01, about 0.05, about 0.1, about 0.15, about 0.2, about0.3, about 0.4, or about 0.5. In some cases, the ratio of the area ofthe aperture to the area of the housing is less than or equal to about0.001, less than or equal to about 0.005, less than or equal to about0.01, less than or equal to about 0.05, less than or equal to about 0.1,less than or equal to about 0.15, less than or equal to about 0.2, orless than or equal to about 0.3, less than or equal to about 0.4, orless than or equal to about 0.5.

A cell can comprise an electrically conductive housing and a conductorin electrical communication with a current collector. The conductorprotrudes through the housing through an aperture in the housing and maybe electrically isolated from the housing. The ratio of the area of theaperture to the area of the housing may be less than about 0.3, 0.2,0.15, 0.1, 0.05, 0.01, 0.005, or 0.001 (e.g., less than about 0.1).

A cell housing can comprise an electrically conductive container and aconductor in electrical communication with a current collector. Theconductor can protrude through the container through an aperture in thecontainer and is electrically isolated from the container. The ratio ofthe area of the aperture to the area of the container may be less thanabout 0.3, 0.2, 0.15, 0.1, 0.05, 0.01, 0.005, or 0.001 (e.g., less thanabout 0.1). The housing can be capable of enclosing a cell that iscapable of storing, taking in, discharging, and/or returning less thanabout 100 Wh of energy, about 100 Wh of energy, or more than about 100Wh of energy. The housing can be capable of enclosing a cell that iscapable of storing, taking in, discharging, and/or returning at leastabout 25 Wh of energy. The cell can be capable of storing, taking in,discharging, and/or returning at least about 1 Wh, 5 Wh, 25 Wh, 50 Wh,100 Wh, 500 Wh, 1 kWh, 1.5 kWh, 2 kWh, 3 kWh, 5 kWh, 10 kWh, 15 kWh, 20kWh, 30 kWh, 40 kWh, or 50 kWh of energy.

FIG. 3 is a cross-sectional side view of an electrochemical cell orbattery 300 comprising a housing 301, an electrically conductivefeed-through (i.e., conductor, such as a conductor rod) 302 that passesthrough an aperture in the housing and is in electrical communicationwith a liquid metal negative electrode 303, a liquid metal positiveelectrode 305, and a liquid salt electrolyte 304 between the liquidmetal electrodes 303, 305. The cell or battery 300 can be configured foruse with cell chemistries operated under a low voltage mode (“Type 1mode”) or high voltage mode (“Type 2 mode”), as disclosed elsewhereherein. The conductor 302 may be electrically isolated from the housing301 (e.g., using electrically insulating seals). The negative currentcollector 307 may comprise foam material 303 that behaves like a sponge,and the negative electrode liquid metal soaks into the foam. The liquidmetal negative electrode 303 is in contact with the molten saltelectrolyte 304. The liquid salt electrolyte is also in contact with thepositive liquid metal electrode 305. The positive liquid metal electrode305 can be in electrical communication with the housing 301 along theside walls and/or along the bottom end wall of the housing.

The housing may include a container and a container lid (e.g., cellcap). The container and container lid may be connected mechanically(e.g., welded). In some cases, the mechanical connection may comprise achemical connection. In some instances, the container lid iselectrically isolated from the container. The cell lid may or may not beelectrically isolated from the negative current lead in such instances.In some instances, the container lid is electrically connected to thecontainer (e.g., cell body). The cell lid may then be electricallyisolated from the negative current lead. During operation (e.g., when ina molten state), the container lid and the container can be connectedelectronically (e.g., through a direct electrical connection, such as,for example, via a welded lid-to-cell body joint, or ionically throughthe electrolyte and the electrodes). The negative current lead may beelectrically isolated from the container and/or container lid (e.g.,cell cap), via, for example, the use of an electrically insulatinghermetic seal. In some examples, an electrically insulating barrier(e.g., seal) may be provided between the negative current lead and thecontainer lid. As an alternative, the seal can be in the form of agasket, for example, and placed between the container lid, and thecontainer. In some examples, the electrochemical cell or battery 300 maycomprise two or more conductors passing through one or more aperturesand in electrical communication with the liquid metal negative electrode303. In some instances, a separator structure (not shown) may bearranged within the electrolyte 304 between the liquid negativeelectrode 303 and the (liquid) positive electrode 305.

The housing 301 can be constructed from an electrically conductivematerial such as, for example, steel, iron, stainless steel, low carbonsteel, graphite, nickel, nickel based alloys, titanium, aluminum,molybdenum, tungsten, or conductive compounds such as nitrides (e.g.,silicon carbide or titanium carbide), or a combination thereof (e.g.,alloy).

The housing 301 may comprise a housing interior 306. The housinginterior 306 may include, but is not limited to, a sheath (e.g., agraphite sheath), a coating, a crucible (e.g., a graphite crucible), asurface treatment, a lining, or any combination thereof). In oneexample, the housing interior 306 is a sheath. In another example, thehousing interior 306 is a crucible. In yet another example, the housinginterior 306 is a coating or surface treatment. The housing interior 306may be thermally conductive, thermally insulating, electricallyconductive, electrically insulating, or any combination thereof. In somecases, the housing interior 306 may be provided for protection of thehousing (e.g., for protecting the stainless steel material of thehousing from corrosion). In some cases, the housing interior can beanti-wetting to the liquid metal positive electrode. In some cases, thehousing interior can be anti-wetting to the liquid electrolyte.

The housing may comprise a lining component (e.g., a lining componentthat is thinner than the cell body) of a separate metal or compound, ora coating (e.g., an electrically conductive coating), such as, forexample, a steel housing with a graphite lining, or a steel housing witha nitride coating or lining (e.g., boron nitride, aluminum nitride), atitanium coating or lining, or a carbide coating or lining (e.g.,silicon carbide, titanium carbide). The coating can exhibit favorableproperties and functions, including surfaces that are anti-wetting tothe positive electrode liquid metal. In some cases, the lining (e.g.,graphite lining) can be dried by heating above room temperature in airor dried in a vacuum oven before or after being placed inside the cellhousing. Drying or heating the lining can remove moisture from thelining prior to adding the electrolyte, positive electrode, or negativeelectrode to the cell housing.

The housing 301 may include a thermally and/or electrically insulatingsheath or crucible 306. In this configuration, the negative electrode303 may extend laterally between the side walls of the housing 301defined by the sheath or crucible without being electrically connected(i.e., shorted) to the positive electrode 305. Alternatively, thenegative electrode 303 may extend laterally between a first negativeelectrode end 303 a and a second negative electrode end 303 b. When thesheath or crucible 306 is not provided, the negative electrode 303 mayhave a diameter (or other characteristic dimension, illustrated in FIG.3 as the distance from 303 a to 303 b) that is less than the diameter(or other characteristic dimension such as width for a cuboid container,illustrated in FIG. 3 as the distance D) of the cavity defined by thehousing 301.

The crucible can be made to be in electronic contact with the cellhousing using a thin layer of a conductive liquid metal or semi-solidmetal alloy located between the crucible and the cell housing, such asthe elements Pb, Sn, Sb, Bi, Ga, In, Te, or a combination thereof.

The housing interior (e.g., sheath, crucible and/or coating) 306 can beconstructed from a thermally insulating, thermally conductive, and/orelectrically insulating or electrically conductive material such as, forexample, graphite, carbide (e.g., SiC, TiC), nitride (e.g., BN),alumina, titania, silica, magnesia, boron nitride, or a mixed oxide,such as, for example, calcium oxide, aluminum oxide, silicon oxide,lithium oxide, magnesium oxide, etc. For example, as shown in FIG. 3 ,the sheath (or other) housing interior 306 has an annularcross-sectional geometry that can extend laterally between a firstsheath end 306 a and a second sheath end 306 b. The sheath may bedimensioned (illustrated in FIG. 3 as the distance from 306 a to 306 b)such that the sheath is in contact and pressed up against the side wallsof the cavity defined by the housing cavity 301. As an alternative, thehousing interior 306 can be used to prevent corrosion of the containerand/or prevent wetting of the cathode material up the side wall, and maybe constructed out of an electronically conductive material, such assteel, stainless steel, tungsten, molybdenum, nickel, nickel basedalloys, graphite, titanium, or titanium nitride. For example, the sheathmay be very thin and may be a coating. The coating can cover just theinside of the walls, and/or, can also cover the bottom of the inside ofthe container. In some cases, the sheath (e.g., graphite sheath) may bedried by heating above room temperature in air or dried in a vacuum ovenbefore or after being placed inside the cell housing. Drying or heatingthe lining may remove moisture from the lining prior to adding theelectrolyte, positive electrode, or negative electrode to the cellhousing.

A cell can include an electrically insulating or electricallyconductive, and chemically stable sheath or coating between one or morewalls of the cell and the negative electrode, electrolyte and/orpositive electrode to minimize or prevent shorting to the one or morewalls of the cell. In some cases, the cell can be formed of anon-ferrous container or container lining, such as a carbon-containingmaterial (e.g., graphite), or a carbide (e.g., SiC, TiC), or a nitride(e.g., TiN, BN), or a chemically stable metal (e.g., Ti, Ni, B). Thecontainer or container lining material may be electrically conductive.

Instead of a sheath, the cell may comprise an electrically conductivecrucible or coating that lines the side walls and bottom inner surfaceof the cell housing, referred to as a cell housing liner, preventingdirect contact of the positive electrode with the cell housing. The cellhousing liner may prevent wetting of the positive electrode between thecell housing and the cell housing liner or sheath and may prevent directcontact of the positive electrode on the bottom surface of the cellhousing. The sheath may be very thin and can be a coating. The coatingcan cover just the inside of the walls, and/or, can also cover thebottom of the inside of the container. The sheath may not fit perfectlywith the housing 301 which may hinder the flow of current between thecell lining and the cell housing. To ensure adequate electronicconduction between the cell housing and the cell lining, a liquid ofmetal that has a low melting point (e.g., Pb, Sn, Bi), can be used toprovide a strong electrical connection between the sheath/coating andthe cell housing. This layer can allow for easier fabrication andassembly of the cell.

The housing 301 can also include a first (e.g., negative) currentcollector or lead 307 and a second (e.g., positive) current collector308. The negative current collector 307 may be constructed from anelectrically conductive material such as, for example, nickel-iron(Ni—Fe) foam, perforated steel disk, sheets of corrugated steel, sheetsof expanded metal mesh, etc. The negative current collector 307 may beconfigured as a plate or foam that can extend laterally between a firstcollector end 307 a and a second collector end 307 b. The negativecurrent collector 307 may have a collector diameter that is less than orsimilar to the diameter of the cavity defined by the housing 301. Insome cases, the negative current collector 307 may have a collectordiameter (or other characteristic dimension, illustrated in FIG. 3 asthe distance from 307 a to 307 b) that is less than or similar to thediameter (or other characteristic dimension, illustrated in FIG. 3 asthe distance from 303 a to 303 b) of the negative electrode 303. Thepositive current collector 308 may be configured as part of the housing301; for example, the bottom end wall of the housing may be configuredas the positive current collector 308, as illustrated in FIG. 3 .Alternatively, the current collector may be discrete from the housingand may be electrically connected to the housing. In some cases, thepositive current collector may not be electrically connected to thehousing. The present disclosure is not limited to any particularconfigurations of the negative and/or positive current collectorconfigurations.

The negative electrode 303 can be contained within the negative currentcollector (e.g., foam) 307. In this configuration, the electrolyte layercomes up in contact with the bottom, sides, and/or the top of the foam307. The metal contained in the foam (i.e., the negative electrodematerial) can be held away from the sidewalls of the housing 301, suchas, for example, by the absorption and retention of the liquid metalnegative electrode into the foam, thus allowing the cell to run withoutthe insulating sheath 306. In some cases, a graphite sheath or graphitecell housing liner (e.g., graphite crucible) may be used to prevent thepositive electrode from wetting up along the side walls, which canprevent shorting of the cell.

Current may be distributed substantially evenly across a positive and/ornegative liquid metal electrode in contact with an electrolyte along asurface (i.e., the current flowing across the surface may be uniformsuch that the current flowing through any portion of the surface doesnot substantially deviate from an average current density). In someexamples, the maximum density of current flowing across an area of thesurface is less than about 105%, or less than or equal to about 115%,less than or equal to about 125%, less than or equal to about 150%, lessthan or equal to about 175%, less than or equal to about 200%, less thanor equal to about 250%, or less than or equal to about 300% of theaverage density of current flowing across the surface. In some examples,the minimum density of current flowing across an area of the surface isgreater than or equal to about 50%, greater than or equal to about 60%,greater than or equal to about 70%, greater than or equal to about 80%,greater than or equal to about 90%, or greater than or equal to about95% of the average density of current flowing across the surface.

Viewed from a top or bottom direction, as indicated respectively by “TOPVIEW” and “BOTTOM VIEW” in FIG. 3 , the cross-sectional geometry of thecell or battery 300 can be circular, elliptical, square, rectangular,polygonal, curved, symmetric, asymmetric or any other compound shapebased on design requirements for the battery. In an example, the cell orbattery 300 is axially symmetric with a circular or squarecross-section. Components of cell or battery 300 (e.g., component inFIG. 3 ) may be arranged within the cell or battery in an axiallysymmetric fashion. In some cases, one or more components may be arrangedasymmetrically, such as, for example, off the center of the axis 309.

The combined volume of positive and negative electrode material may beat least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95%of the volume of the battery (e.g., as defined by the outer-most housingof the battery, such as a shipping container). In some cases, thecombined volume of anode and cathode material is at least about 5%, atleast about 10%, at least about 20%, at least about 30%, at least about40%, at least about 60%, at least about 75%, of the volume of the cell.The combined volume of the positive and negative electrodes material mayincrease or decrease (e.g., in height) during operation due to growth orexpansion, or shrinkage or contraction, respectively, of the positive ornegative electrode. In an example, during discharge, the volume of thenegative electrode (anode during discharge) may be reduced due totransfer of the negative electrode material to the positive electrode(cathode during discharge), wherein the volume of the positive electrodeis increased (e.g., as a result of an alloying reaction). The volumereduction of the negative electrode may or may not equal the volumeincrease of the positive electrode. The positive and negative electrodematerials may react with each other to form a solid or semi-solid mutualreaction compound (also “mutual reaction product” herein), which mayhave a density that is the same, lower, or higher than the densities ofthe positive and/or negative electrode materials. Although the mass ofmaterial in the electrochemical cell or battery 300 may be constant,one, two or more phases (e.g., liquid or solid) may be present, and eachsuch phase may comprise a certain material composition (e.g., an alkalimetal may be present in the materials and phases of the cell at varyingconcentrations: a liquid metal negative electrode may contain a highconcentration of an alkali metal, a liquid metal positive electrode maycontain an alloy of the alkali metal and the concentration of the alkalimetal may vary during operation, and a mutual reaction product of thepositive and negative liquid metal electrodes may contain the alkalimetal at a fixed or variable stoichiometry). The phases and/or materialsmay have different densities. As material is transferred between thephases and/or materials of the electrodes, a change in combinedelectrode volume may result.

In some cases, a cell can include one or more alloyed products that areliquid, semi-liquid (or semi-solid), or solid. The alloyed products canbe immiscible (or, in some cases, soluble) with the negative electrode,positive electrode and/or electrolyte. The alloyed products can formfrom electrochemical processes during charging or discharging of a cell.

An alloyed product can include an element constituent of a negativeelectrode, positive electrode and/or electrolyte. An alloyed product canhave a different density than the negative electrode, positive electrodeor electrolyte, or a density that is similar or substantially the same.The location of the alloyed product can be a function of the density ofthe alloyed product compared to the densities of the negative electrode,electrolyte and positive electrode. The alloyed product can be situatedin the negative electrode, positive electrode or electrolyte, or at alocation (e.g., interface) between the negative electrode and theelectrolyte or between the positive electrode and the electrolyte, orany combination thereof. In an example, an alloyed product is anintermetallic between the positive electrode and the electrolyte (see,for example, FIG. 4 ). In some cases, some electrolyte can seep inbetween the intermetallic and the positive electrode. In other examples,the alloyed product can be at other locations within the cell and beformed of a material of different stoichiometries/compositions,depending on the chemistry, temperature, and/or charge state of thecell.

FIG. 4 is a cross-sectional side view of an electrochemical cell orbattery 400 with an intermetallic layer 410. The intermetallic layer 410can include a mutual reaction compound of a material originating fromthe negative electrode 403 and positive electrode material 405. Forexample, a negative liquid metal electrode 403 can comprise an alkali oralkaline earth metal (e.g., Na, Li, K, Mg, or Ca), the positive liquidmetal electrode 405 can comprise one or more of transition metal,d-block (e.g., Group 12), Group IIIA, IVA, VA or VIA elements (e.g.,lead and/or antimony and/or bismuth), and the intermetallic layer 410can comprise a mutual reaction compound or product thereof (e.g., alkaliplumbide, antimonide or bismuthide, e.g., Na₃Pb, Li₃Sb, K₃Sb, Mg₃Sb₂,Ca₃Sb₂, or Ca₃Bi₂). An upper interface 410 a of the intermetallic layer410 is in contact with the electrolyte 404, and a lower interface 410 bof the intermetallic layer 410 is in contact with the positive electrode405. The mutual reaction compound may be formed during discharging at aninterface between a positive liquid metal electrode (liquid metalcathode in this configuration) 405 and a liquid salt electrolyte 404.The mutual reaction compound (or product) can be solid or semi-solid. Inan example, the intermetallic layer 410 can form at the interfacebetween the liquid metal cathode 405 and the liquid salt electrolyte404. In some cases, the intermetallic layer 410 may exhibit liquidproperties (e.g., the intermetallic may be semi-solid, or it may be of ahigher viscosity or density than one or more adjacent phases/materials).

The cell 400 comprises a first current collector 407 and a secondcurrent collector 408. The first current collector 407 is in contactwith the negative electrode 403, and the second current collector 408 isin contact with the positive electrode 405. The first current collector407 is in contact with an electrically conductive feed-through 402. Ahousing 401 of the cell 400 can include a thermally and/or electricallyinsulating sheath 406. In an example, the negative liquid metalelectrode 403 includes magnesium (Mg), the positive liquid metalelectrode 405 includes antimony (Sb), and the intermetallic layer 410includes Mg and Sb (Mg_(x)Sb, where ‘x’ is a number greater than zero),such as, for example, magnesium antimonide (Mg₃Sb₂). Cells with a Mg∥Sbchemistry may contain magnesium ions within the electrolyte as well asother salts (e.g., MgCl₂, NaCl, KCl, or a combination thereof). In somecases, in a discharged state, the cell is deficient in Mg in thenegative electrode and the positive electrode comprises and alloy ofMg—Sb. In such cases, during charging, Mg is supplied from the positiveelectrode, passes through the electrolyte as a positive ion, anddeposits onto the negative current collector as Mg. In some examples,the cell has an operating temperature of at least about 550° C., 600°C., 650° C., 700° C., or 750° C., and in some cases between about 650°C. and about 750° C. In a charged state, all or substantially all thecomponents of the cell can be in a liquid state. Alternative chemistriesexist, including Ca-Mg∥Bi comprising a calcium halide constituent in theelectrolyte (e.g., CaF₂, KF, LiF, CaCl₂), KCl, LiCl, CaBr₂, KBr, LiBr,or combinations thereof) and operating above about 500° C., Ca-Mg∥Sb-Pbcomprising a calcium halide constituent in the electrolyte (e.g., CaF₂,KF, LiF, CaCl₂), KCl, LiCl, CaBr₂, KBr, LiBr, or combinations thereof)and operating above about 500° C., Li∥Pb-Sb cells comprising alithium-ion containing halide electrolyte (e.g., LiF, LiCl, LiBr, orcombinations thereof) and operating between about 350° C. and about 550°C., and Na∥Pb cells comprising a sodium halide as part of theelectrolyte (e.g., NaCl, NaBr, NaI, NaF, LiCl, LiF, LiBr, LiI, KCl, KBr,KF, KI, CaCl₂), CaF₂, CaBr₂, CaI₂, or combinations thereof) andoperating above about 300° C. In some cases, the product of thedischarge reaction may be an intermetallic compound (e.g., Mg₃Sb₂ forthe Mg∥Sb cell chemistry, Li₃Sb for the Li∥Pb-Sb chemistry, Ca₃Bi₂ forthe Ca-Mg∥Bi chemistry, or Ca₃Sb₂ for the Ca-Mg∥Pb-Sb chemistry), wherethe intermetallic layer may develop as a distinct solid phase by, forexample, growing and expanding horizontally along a direction x and/orgrowing or expanding vertically along a direction y at the interfacebetween the positive electrode and the electrolyte. The growth may beaxially symmetrical or asymmetrical with respect to an axis of symmetry409 located at the center of the cell or battery 400. In some cases, theintermetallic layer is observed under Type 1 mode of operation but notType 2 mode of operation. For example, the intermetallic layer (e.g.,the intermetallic layer in FIG. 4 ) may not form during operation of aType 2 cell.

Wired or wire-less interconnections may be formed between individualelectrochemical cells and/or between groups of electrochemical cells(e.g., modules, towers, packs, trays, cores, CEs, systems, or any othergroup comprising one or more electrochemical cells). In some cases,groups of cells may be joined via one or more cell-to-cellinterconnections. In some cases, groups of cells may be joined via agroup-level interconnection. The group-level interconnection may furthercomprise one or more interconnections with one or more individual cellsof the group. The interconnections may be structural and/or electrical.Cells and/or groups of cells may be assembled (or stacked) horizontallyor vertically. Such assembled cells and/or groups of cells may bearranged in series or parallel configurations. Further, groups of cellsmay be supported by various frames. The frames may provide structuralsupport, participate or aid in forming the interconnections (e.g.,frames on groups of cells may mate or be connected), and/or be part of athermal management system (e.g., in concert with a thermal managementframe). For example, an interconnection may be structural, electricaland/or thermal.

The electrochemical cells can be arranged in series and/or parallel toform an electrochemical energy storage system (e.g., battery). Theenergy storage system can comprise modules, packs, cores, CEs and/orsystems of electrochemical cells surrounded by a frame (e.g., a framethat can be used for both structural support and thermal management ofthe system).

FIG. 5 shows an example of a cell pack 500 comprising 3 modules 505.Each of the modules comprises 12 cells 530 that are connected inparallel 510. The modules are held in place with cell pack framing (also“frame” herein) 515 that includes a top component of the frame 520. Thecells are stacked directly on top of each other with the negativecurrent terminal of one cell 525 contacted directly with the housing ofanother cell (e.g., the cell above it). The negative current terminalsof the top layer of cells will have no housing of another cell directlyabove, so can instead be contacted (e.g., brazed to, welded to) anegative busbar 535.

In some configurations, the parallel connections 510 made in the modulecan be created using a single piece (or component) with multiple pocketsfor cell materials. This piece can be a stamped component that allowsfor direct electrical connection between cells. In some examples, thestamped pocketed electrically conductive housing does not create abarrier between the cells. In some cases, the pocketed electricallyconductive housing seals the pockets from each other. This electricallyconductive housing can be easier to manufacture and assemble thanindividual electrically conductive cell housings. In someconfigurations, the parallel connections 510 made in the module can becreated by direct contact of the housings of the cells in the module.

When stacked vertically, the electrochemical cells bear the weight ofthe cells stacked above. The cells can be constructed to support thisweight. In some cases, cell-to-cell spacers 640 are placed between thelayers of cells. These spacers can disperse the weight of the abovecells and/or relieve some of the weight applied to the negative currentterminals. In some cases, the negative current terminals areelectrically isolated from the housing with a seal. This seal can be theweakest structural component of the electrochemical cell, so the spacerscan reduce the amount of force applied to the seals.

In some implementations, a liquid metal battery comprises a plurality ofelectrochemical cells each comprising an electrically conductive housingand a conductor in electrical communication with a current collector.The electrically conductive housing can comprise a negative electrode,electrolyte and positive electrode that are in a liquid state at anoperating temperature of the cell. The conductor can protrude throughthe electrically conductive housing through an aperture in theelectrically conductive housing and can be electrically isolated fromthe electrically conductive housing with a seal. The plurality ofelectrochemical cells can be stacked in series with the conductor of afirst cell in electrical contact with the electrically conductivehousing of a second cell. The liquid metal battery can also comprise aplurality of non-gaseous spacers disposed between the electrochemicalcells. In some cases, the electrochemical cells are stacked vertically.For example, at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 36,40, 48, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 216, 250, 256,300, 350, 400, 450, 500, 750, 1000, 1500, 2000 or more electrochemicalcells can be stacked in series. In some cases, the battery furthercomprises at least one additional electrochemical cell connected inparallel to each of the plurality of electrochemical cells that arestacked in series. For example, each vertically stacked cell can beconnected in parallel with at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15,16, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200,250, 300, 350, 400, 450, 500, 750, 1000, 1500, 2000 or more additionalelectrochemical cells. In some cases, the electrically conductivehousings are part of a current conducting pathway.

The non-gaseous spacers (also “spacers” herein) can be a solid material.In some cases, the spacers comprise a ceramic material. Non-limitingexamples of ceramic materials include aluminum nitride (AlN), boronnitride (BN), yttrium oxide (Y₂O₃), zirconium oxide (ZrO₂), yttriapartially stabilized zirconia (YPSZ), aluminum oxide (Al₂O₃),chalcogenides, erbium oxide (Er₂O₃), silicon dioxide (SiO₂), quartz,glass, or any combination thereof. In some cases, the spacers areelectrically insulating. The spacers can have any suitable thickness. Insome cases, the thickness of the spacer is approximately equal to thedistance that the conductor protrudes out of the electrically conductivehousing (e.g., the thickness of the spacer can be within about 0.005%,about 0.01%, about 0.05%, about 0.1% or about 0.5% of the distance thatthe conductor protrudes out of the electrically conductive housing).

The cell to cell connections can be configured in a variety of waysbased on tolerances and optimal conductive path. In one configuration,the top face of the negative current lead in one cell can be directlyjoined (e.g., brazed, welded) to the bottom of the cell above it (see,for example, FIG. 6 ). Other configurations can include, for example,alternative directly joined (e.g., alternative braze joined)configurations, such as an outer diameter braze enhanced by differencesin the coefficient of thermal expansion (CTE) of an inner rod and anouter fixture. For example, two cells can be connected by a conductor ofa first cell that sits in a recessed portion of an electricallyconductive housing of a second cell, where the CTE of the conductor isgreater than the CTE of the electrically conductive housing.

In some cases, as shown in FIG. 6 , the conductor 605 of a first cell610 is brazed 615 to the electrically conductive housing 620 of thesecond cell 625. The braze material can be any suitable material. Somenon-limiting examples of braze materials include materials that compriseiron (Fe), nickel (Ni), titanium (Ti), chromium (Cr), zirconium (Zr),phosphorus (P), boron (B), carbon (C), silicon (Si), or any combinationthereof. The cell can comprise a cathode 630, an electrolyte 635 and ananode 640 connected to the current collector and conductor 605. Theconductor can feed through the cell lid 650. In some cases, the cell hassome empty head space 645.

In some implementations, the conductor 605 can feed through a seal 660in the cell lid 650. The conductor (e.g., negative current lead) 605 mayrigid. The seal 660 may not be rigid. As additional cells are addedduring assembly, an increasing weight can be exerted on the conductor605 of the bottom cell 610 by the housing 620 of the top cell 625 (e.g.,at the position 615). In some instances, the vertical spacing betweenthe cells 610 and 625 may decrease if the seal 660 (with the conductor605 and the anode 640) move downward into the cell 610 as a result ofthe compression force. To ensure that modules are electrically isolatedfrom each other, spacers (e.g., ceramics) 655 can be placed across thesurface of the cells to support the cells above them. In thisconfiguration, the cell housing can be used as the main structuralsupport for the system. The ceramic spacer 655 can relieve the seal 660from having to support the weight of the top cell 625 (and anyadditional cells added during assembly). In some configurations, theremay initially be a gap between the top of the spacers 655 and the bottomof the housing 620 of the top cell 625 (e.g., the thickness of thespacer can be slightly less than the distance that the conductorinitially protrudes through the electrically conductive housing), andthe spacers (e.g., ceramics) can be placed in compression duringassembly as additional cell(s) are added (e.g., as the spacing betweenthe top of the housing of the bottom cell 610 and the bottom of thehousing of the top cell 625 decreases). As a result, the displacement(also “anode-cathode displacement” herein) between anodes and cathodes(e.g., final displacement after assembly between the anode 640 and thecathode 630 in cell 610) can in some cases be determined by thenon-gaseous spacers. In some configurations, the spacers can be placedin compression right away (e.g., if the thickness of the spacer isslightly greater than the distance that the conductor initiallyprotrudes through the electrically conductive housing).

Cells stacked vertically in series can be attached through a direct(e.g., hard) electrical connection such that the height from 650 to 640and/or anode-cathode displacement (ACD) can be determined by thedimensional tolerance of 655. In some examples, the height from 650 to640 can be at least about 3 millimeters (mm), at least about 5 mm, atleast about 7 mm, at least about 10 mm, at least about 15 mm, and thelike. In some examples, the ACD can be about 3 mm, about 5 mm, about 7mm, about 10 mm, about 15 mm, or greater. FIG. 6 is an example of howsuch connections may be configured.

Cells stacked vertically in series can be connected using a directelectrical connection such that resistance per cell connection isreduced, for example, below about 100 milli-Ohm (mOhm), 10 mOhm, 1 mOhm,or 0.1 mOhm. FIG. 6 is an example of how such connections may beconfigured. FIG. 6 also provides an example of a CTE mismatched sealconnection.

Cell packs can be attached in series and parallel in variousconfigurations to produce cores, CEs, or systems. The number andarrangement of various groups of electrochemical cells can be chosen tocreate the desired system voltage and energy storage capacity. Thepacks, cores, CEs, or systems can then be enclosed together in hightemperature insulation to create a system that can heat itself using theenergy provided (e.g., rejected) from cells during charging and/ordischarging. For example, FIG. 7 is an example of how packs can beconfigured, indicating that the cell packs in a given plane areconnected to one another in parallel or in series 705, while the packsconnected directly atop one another are connected in series 710.

The packs themselves can be connected vertically and horizontally to oneanother through one or more busbars (e.g., unlike the cell-to-cellconnections within a pack which can be direct connections such as brazesor welds). In some cases, the busbar is flexible or comprises a flexiblesection (e.g., to accommodate non-isothermal expansion of the systemthroughout heat up and operation). In some cases, the busbar comprisesor is connected via a compliant interconnection component (e.g., braidedmetal or metal alloy, or bent sheet metal) that may or may not comprisethe same material as the (rest of the) busbar. The busbar and/or thecompliant interconnection component can comprise a conductive material(e.g., stainless steel, nickel, copper, aluminum-copper based alloy, orany combination thereof). The pack may further comprise or form other oradditional interconnections (e.g., to allow the pack to beinterconnected with additional packs). In some implementations, busbarsmay be used to provide pack-level electricalconnections/interconnections (e.g., only busbars may be used forpack-level electrical connections/interconnections).

A busbar can be used to make an electrical connection with cells in aparallel string (e.g., a parallel string of cells, a parallel string ofpacks, etc.). In some examples, a busbar can be used to configure a setof cells or cell modules into a parallel string configuration by beingelectrically connected with the same terminal on all of the cells orcell modules (e.g., the negative terminals of all of the cells or cellmodules, or the positive terminals of all of the cell or cell modules).For example, a positive busbar and/or a negative busbar may be used. Thepositive busbar can be connected to the housing and may or may not needto be flexible. In some cases, the positive busbar may not be used. Thenegative busbar can be joined to features in (or on) one or more of thecell bodies (e.g., the cell bodies of individual cells in a pack) toprovide a strong electrical connection. In some cases, the negativebusbar can be attached to conductive feed-throughs (e.g., negativecurrent leads), which may require some compliance for thermal expansion.For example, a flexible connection between a relatively rigid busbarcore and the feed-through may be achieved using a compliance feature(e.g., a spiral pattern comprising one or multiple spiral arms) betweenthe feed-through and the busbar. In some cases, the busbar may besufficiently compliant such that the compliance feature is not needed.In configurations where cells are stacked vertically atop one another,the busbar at the top of the cell stack (e.g., cell pack stack) cancomprise only the negative busbar (e.g., since the positive terminal ofthe stack can be on the bottom cell in the stack).

The core may be designed with multiple packs electrically connected inseries and/or in parallel. The packs that are part of the core may becontained (e.g., all contained) within a single thermally managedchamber (also “thermal chamber” herein). For example, thermal insulationmay surround a set of packs, thus maintaining (e.g., keeping) the packs(e.g., all packs) in good thermal contact with each other and thermallyinsulating the packs (e.g., all of the packs) from ambient conditions.In some cases, the core comprises electrically powered heaters installednear an inner surface of at least a portion of the insulation,electrically powered heaters distributed throughout the internal heatedzone and/or connected to cell packs, or a combination thereof. The coremay further comprise a frame (e.g., an internal metal frame). In somecases, the packs are arranged on trays that are arranged in a verticaland/or a horizontal stack. Each tray can provide mechanical support forthe packs (e.g., the tray can comprise a frame). A plurality of trays(e.g., 2, 3, 4, 5, 10, 15, 20, 25, 30 or more trays) can be assembledinto a core. The trays can be supported with the internal metal frame inthe core.

Thermal insulation and/or frames may be provided with various groups ofcells herein. The thermal insulation and/or the frame(s) may beconfigured to allow a group of cells to be cooled, the insulation to beremoved, and individual or sets of subgroups of cells (or individualcells) to be disconnected, removed and/or replaced. For example, thethermal insulation and/or the frame may be designed to allow the core(and/or any system of the disclosure) to be cooled, the insulation to beremoved, individual or sets of packs to be disconnected and removed fromthe core to allow for a single pack to be disconnected, removed andreplaced, or any combination thereof. In some cases, a tray can bedisconnected and removed from the core to allow for a single pack to bedisconnected, removed and replaced, or any combination thereof. The corecan then be reassembled and heated back up to operating temperature toallow for resumed operation. The thermal insulation and/or frames mayfurther be configured to allow thermal management (e.g., modular thermalmanagement) of individual cells or portion(s) thereof, groups of cells,or devices or systems comprising such cell(s).

Thermal Management

Elevated or high temperatures systems/devices (e.g., energy storagedevices such as, for example, batteries) of the disclosure can comprisethermal management systems. In some cases, elevated temperature devicesmay be high temperature devices, and vice versa. In some examples, theenergy storage system/device can comprise a plurality of electrochemicalcells. Each electrochemical cell can comprise a negative electrode, anelectrolyte and a positive electrode. At least one of the negativeelectrode, the electrolyte and the positive electrode can be in a liquidstate at an operating temperature of the electrochemical cell.

In some implementations, thermal management of the devices (e.g.,batteries) herein may include over-insulating (providing excessinsulation) and cooling during normal operation. Heating can beperformed at start-up of the device. For example, heating can beperformed at start-up of a battery system that comprises a batterycomprising one or more cells that may be organized in one or more groupsof cells (e.g., for at least one of the metal electrodes and/or theelectrolyte in the one or more cells to melt and/or for the battery tofunction). Heating may be achieved using any form of heaters, such as,for example, electrical resistance heaters that convert electricalenergy from a power source (e.g., power generators via the electricpower grid, back-up battery system, an on-site power generator such as adiesel generator, renewable power generators such as a wind turbine or asolar power system). Heating can also be provided to the system after ithas been heated up in order to manage the temperature of the systemduring charging, discharging, and/or rest operating modes, or duringperiods of extended resting or during periods where the battery ischarged and/or discharged at power rates below its regular (or normal)or intended operating power rates. When the battery is at, near or aboveits operating temperature, the battery may be able to keep itself warmby providing power from energy stored within the battery (e.g., thebattery may discharge its energy to its own heaters). Battery insulationcan be designed such that, once heated, the battery retains heat (e.g.,in a thermal chamber of the battery) during idle time (e.g., when thebattery is not charging or discharging). However, when the battery isoperating, the thermal chamber may in some cases overheat. To regulatethe temperature of the device (e.g., the temperature in the devicechamber or container) during the cycling period (e.g., when the batteryis charging and/or discharging), a thermal management system can be used(e.g., to cool hot zones). As cell components may require heat foroperation, the system may be configured such that the cells and/orgroups of cells (e.g., packs) are thermally insulated in excess to trapand retain as much heat as possible, while providing mechanism(s) fornatural or forced movement of one or more thermal management fluids tohelp maintain given (e.g., optimal) thermal boundaries. The mechanism(s)may be activated by the thermal management system. Such activatedcooling mechanisms may enable improved system reliability, performancerobustness, and high efficiency operation. In some cases, the coolingmechanism(s) may comprise activated passive cooling (e.g., openingvents/convection flow channels, opening a vent/valve to allow naturalconvection to cool the system). In some cases, the cooling mechanism(s)may comprise active cooling (e.g., starting or increasing a flow of athermal management fluid). In some cases, the cooling mechanism maycomprise a combination of activated passive cooling and active cooling.

In an example, the system comprises an amount of insulation that enablesthe system to increase an internal temperature of the system above anoperating temperature of the system (e.g., above the standard operatingtemperature) during regular operation. The system may maintain theinternal temperature at about, or within less than about 10° C., 20° C.,50° C., 100° C. or 200° C. of a given (e.g., desired) operatingtemperature by activating an actuator, such as, for example, a valve ora lift-gate, to allow a fluid (e.g., thermal management fluid) to flowthrough one or more fluid flow paths driven by natural convection. Thesystem may be self-heated under normal/regular operation, and may needto be cooled via activated passive cooling to maintain its operatingtemperature.

In some implementations, the thermal management system may provide amechanism for emergency cool-down (e.g., in a condition where emergencyshut-down of the battery system is required, such as, for example, dueto a natural disaster in the deployed region). Emergency cool-down maybe triggered by a thermal management computer system when it receivesone or more specific signals. Such signal(s) may comprise signal(s)received from within the system (e.g., battery system or a larger systemcomprising the battery system) and/or outside signal(s) indicating thatemergency cool-down procedures are to be initiated (e.g., earthquakealert). The emergency cool-down may include one or more mechanisms forrejecting/evacuating heat from the battery system to the thermalmanagement fluid and/or to the environment (e.g., surroundingatmosphere). For example, the emergency cool-down may include increasinga flow rate of the thermal management fluid, partially or fully openingvent(s) or other thermal relief structure(s) in the system, and/orvarying a temperature of the thermal management fluid supplied (in) tothe system such that more thermal energy can be removed from the system.

A thermal management system (e.g., within a battery system) configuredto implement such mechanism(s) can be integrated in a frame (e.g., asupport frame) of the battery, allowing thermal management fluid(s) toflow through the system (e.g., battery system). In some cases, thethermal management fluids may flow through the system (e.g., batterysystem) without touching any cells or cell components. In some cases,such functionality/mechanisms may be integrally formed with (e.g., builtinto) one or more structural members of the battery or a portion thereof(e.g., a structural support member of a core, such as, for example, aframe). In some cases, such functionality/mechanisms may be attached toone or more structural support members (e.g., a structural supportmember of a core). In some cases, the structural support members can bedesigned as dual-purpose components (e.g., providing structural supportand also providing a mechanism for heat evacuation as needed).

During operation of a high temperature system (e.g., core) comprisinghigh temperature cells, cells may generate heat during charging and/ordischarging processes. If a system is operated continuously,sufficiently often and/or with sufficient intensity (e.g., sufficientlyhigh charging/discharging rate) within a given time period, and if thesystem is configured in such a way that the heat generated through thecharging and/or discharging processes can be at least partiallycontained (e.g., through thermal insulation around one or more packs ofcells), such a system may continuously maintain its cells at or aboveits operating temperature without the need to add additional heat (e.g.,through the use of electric heaters). In some cases, the amount of heatgenerated through normal or regular (e.g., intended) operation (e.g.,charge for 5 hours, then rest for 7 hours, then discharge for 5 hours,then rest for 7 hours, repeated daily) may equal the amount of heat lostto the environment.

Normal or regular operation may include or be defined in terms of one ormore charge/discharge operating metrics, such as, for example, overall(e.g., average) charging/discharging rate (e.g., time to fully charge,time to fully discharge), amount of energy charged or discharged (e.g.,change in energy storage capacity upon charging/discharging) and/orenergy efficiency (e.g., energy efficiency over a given time period).Operating parameters (e.g., charge or discharge rate) may fluctuate overtime. The operating metrics may then be provided on an average oroverall basis (e.g., average discharge over a 24-hour period may bespecified even though the discharge rate may fluctuate over time;regardless of charge/discharge profile, the system may have a givencharge/discharge metric when it returns to the same state of charge). Asystem with such charge/discharge metric(s) may be self-heated (e.g.,upon the charging/discharging under such conditions, a portion of theenergy may dissipate due to inefficiencies to provide the necessaryheating), or may use a given amount of additional energy (e.g., lessthan about 10% of energy discharged to the grid) to provide heating.

Normal or regular operation may include charging the system at a ratethat can fully charge the system (e.g., from minimum to full or maximumcharge) in at least about 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6hours, 7 hours, 8 hours, 10 hours, 12 hours, 14 hours, or 20 hours.Normal or regular operation may include discharging the system (e.g.,from full or maximum charge to minimum charge) at a rate that can fullydischarge the system in at least about 1 hour, 2 hours, 3 hours, 4hours, 5 hours, 6 hours, 7 hours, 8 hours, 10 hours, 12 hours, 14 hours,or 20 hours. Normal or regular operation may include charging and/ordischarging the system for a period of less than about 1 hour, less thanabout 2 hours, less than about 4 hours, less than about 6 hours, lessthan about 8 hours, less than about 12 hours, less than about 14 hours,less than about 18 hours, less than about 20 hours, less than about 24hours, less than about 36 hours, or less than about 48 hours. Normal orregular operation may include cumulate charge or energy passed duringcharging and/or discharging (e.g., a single charge and/or dischargecycle, or cumulative energy from several charge/discharge cycles, suchas, for example, by charging 1 Wh, discharging 1 Wh, charging 1.5 Wh anddischarging 1.5 Wh, thereby discharging 2.5 Wh (i.e., 1 Wh+1.5 Wh)overall) the system to release (e.g., to the grid) an amount of energythat is at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%,100%, 110%, 125%, 150%, 175%, 200%, 250%, 300%, 400%, 500%, 750%, 1000%,2000%, 5000%, or 10,000% of its rated energy storage capacity within agiven time period (e.g., less than or equal to about 2 weeks, 1 week, 4days, 48 hours, 24 hours, 12 hours, 8 hours, 4 hours, or 1 hour). Thesystem may release more energy than its rated energy capacity within agiven time period by undergoing multiple partial and/or full dischargeand/or charge cycles within the given time period). Normal or regularoperation may include resting for a given (e.g., some) period betweencharging and/or discharging. The resting period may be less than about 1hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 10hours, 12 hours, 14 hours, 18 hours, 20 hours, 24 hours, 36 hours, or 48hours. The system may be operated at such charge/discharge metrics witha given average efficiency. For example, an overall DC-to-DC energyefficiency may be at least about 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%or 99%. Normal or regular operation may include discharging somecumulative amount of energy (e.g., at least about 50% of its ratedenergy capacity, at least about 80% of its rated energy capacity),charging some cumulative amount of energy (e.g., at least about 50% ofits rated energy capacity, or at least about 80% of its rated energycapacity), not resting for a period or resting for some cumulativeperiod between charge/discharge and/or charge/charge and/orcharge/discharge operational modes (e.g., less than about 20 hours, lessthan about 16 hours), achieving some DC-to-DC round-trip energyefficiency (e.g., less than about 90%, less than about 80%, or less thanabout 70%), and/or operating at such charge/discharge metrics within agiven time period (e.g., less than about 48 hours, or less than about 24hours).

Such a system may be capable of maintaining its cells at or above agiven cell operating temperature (e.g., a target cell operatingtemperature) as long as the system is being operated in this manner.Thus, a battery system can be configured to balance the heat generatedwith the heat released to the environment by providing a suitable amountof insulation and by controlling heat loss through other heat loss paths(e.g., not through insulation but through vents, thermal managementfluid, etc.). In some cases, the battery system can be configured tobalance the heat generated with the heat released to the environment byproviding a suitable amount of insulation, by controlling heat lossthrough other heat loss paths (e.g., not through insulation but throughvents, thermal management fluid, etc.) and by operating the systemregularly (e.g., continuously, often).

In some cases, there can be (e.g., extended) periods of inactivitywithin the cells (e.g., during which the cells are not charging ordischarging). Thermal insulation can be used to prevent heat loss fromthe cells (e.g., to keep the metal electrodes molten when heat is notbeing generated from charging or discharging of the cell). The thermalinsulation may be designed such that it maintains the cells at or aboveoperating temperature for a given period of time (e.g., a finite periodof time, such as, for example, at least about 30 minutes, 1 hour, 2hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 18 hours, 24hours, 2 days, 5 days, 10 days, 20 days, 1 month, or more) when thecells are inactive and/or when no supplemental heating power is providedthrough heaters.

In some cases, a system (e.g., energy storage system such as, forexample, a battery system) may be designed to operate without the needfor heating even when the system is used less regularly and/or lessintensely (e.g., than originally intended or quantified by a systemspecification, than normal or regular operation). A measure of theregularity of operation of the system may in some cases be based onpercentage of use of the system during a given (e.g., specified) timeperiod. For example, the system may be actively charging and/ordischarging for less than or equal to about 99.5%, 99%, 95%, 90%, 85%,80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%,10%, 5%, or less of the given time period (e.g., the battery may be incharging or discharging mode for less than about 20% of the time over athree day period). A measure of the intensity of operation of the systemmay in some cases be based on average charge or discharge power over agiven (e.g., specified) time period as a percentage of its maximum ratedpower capacity. The given time period may include periods of rest (e.g.,0% of rated power). For example, the system may have an average chargeor discharge power of less than or equal to about 99%, 95%, 90%, 80%,70%, 60%, 50%, 40%, 30%, 20%, 10%, 5%, 1%, or less of its rated powerover the given time period. In some examples, the given (e.g.,specified) time period may be equal to or at least about 1 hour, 2hours, 5 hours, 10 hours, 12 hours, 24 hours, 36 hours, 2 days, 3 days,4 days, 5 days, 1 week, 2 weeks or 4 weeks.

The thermal insulation may allow the system to be (e.g., fully)self-heated when operated normally/regularly (e.g., when cycled at leastonce every 2 days, or with at least 50% of its energy capacitydischarged at least every two days). For example, thermal insulation mayenable the system to operate continuously in the self-heatedconfiguration when charged and discharged (or cycled) at least onceevery 2 days. In some examples, the normal/regular operation may includecycling (an example of a charge/discharge metric associated with suchoperation) at least once every 1 day, 2 days, 3 days, 4 days, or thelike.

In such cases (e.g., during periods of inactivity, or when used lessregularly or less intensely), it may be desirable to configure thesystem with an excess amount of insulation (e.g., reduced rate of heatloss) as well as capability to perform activated passive cooling, suchas, for example, opening a valve, lift-gate or other thermal reliefmechanism(s) to increase rate of heat loss and thus preventover-heating. In some cases, cooling channels in the system that cantransport air from outside a thermally maintained zone of the system(e.g., zone comprising the thermal chamber) may be activated such thatair moves through one or more (e.g., dedicated) channels of (e.g.,within) the system. Air heated within the system is allowed to (e.g.,safely) exit the system through one or more channels of the system withor without the use of forced air convection systems (e.g., fans,blowers, air handlers, etc.). In some cases, air transport channels maybe configured to allow natural convection to set in when thermal relieffeatures are activated.

During periods of inactivity, or when used less regularly or lessintensely, the system may continue to operate (or exist in a ‘rest’operational mode and be ready to be charged or discharged) above a giventemperature (e.g., a pre-defined minimum operating temperature limit,such as, for example, at least about 300° C., 350° C., 400° C., 450° C.,475° C., 500° C., 550° C., or 600° C.) without the need to add heat tothe system. Thus, a robust system design of a high temperature batterymay include over-insulating the system and performing activated passivecooling. Such a system configuration may enable more efficient operationduring periods of inactivity and/or during less regular/intense use, andenable efficient operation when operated normally (e.g., as intendedduring periods of activity when cells are charging or discharging and/orduring regular/intense use). Over-insulation and activated passivecooling may in some cases be more efficient (e.g., most advantageouslyemployed) during periods when the system is used less regularly or lessintensely.

The thermal management system may need to dissipate heat generatedduring charging and/or discharging (e.g., using active cooling oractivated passive cooling) to prevent over-heating (e.g., especiallysince the system may be insulated). For example, the thermal managementsystem can be configured to dissipate heat generated duringnormal/regular charging and/or during higher power discharging. In somecases, heat can be added to the system using heaters to keep the systemabove a minimum operating temperature during periods of resting and/orlow intensity operation (e.g., operating at low rates of charging and/ordischarging).

Thermal Management Via Frames

The thermal management system may be implemented with the aid of one ormore structural members of the device configured as conduits forcooling. In some cases, the thermal management system may be implementedwith the aid of one or more frames on the device. Described herein areexamples of frame structures that comprise conduit(s) for thermalmanagement in elevated or high temperatures devices, such as, forexample, high temperature batteries.

An energy storage system of the disclosure can include a framesupporting at least a portion of a plurality of electrochemical cells.The frame can have one or more fluid flow paths for bringing a thermalmanagement fluid in thermal communication with at least a subset of theplurality of electrochemical cells. The thermal management fluid can beany suitable fluid, including but not limited to air, purified/cleanedair, a gas (e.g., helium, argon, supercritical CO₂), oil, water, moltensalt, or steam. Examples of gases are argon or nitrogen. In some cases,ambient air may be used. In some cases, the thermal management fluid hasa high heat capacity.

FIG. 8 shows an example of thermal management fluid being passed througha frame 801 structure of an energy storage device such as, for example,a battery (e.g., a liquid metal battery). The frame may have one or morefunctions (e.g., multiple critical functions) (with) in the device or(with) in a system comprising the device. Examples of such function(s)include, but are not limited to: (i) providing mechanical support to thecells and/or groups of cells (e.g., modules, packs, and/or cores) withinthe device/system, (ii) ensuring cells or groups of cells do notdirectly short to one another or short to grounded connections, (iii)maintaining electrical isolation between cells and/or groups of cells(e.g., modules and/or packs) and other non-electrically activestructural members, and/or (iv) providing a path for thermal managementfluid to flow to aid in thermal management of the battery (or batterysystem). In some cases, the frame 801 can comprise (e.g., be made of)frame elements 805 (e.g., pieces of the frame that can be joinedtogether to make the frame). The frame elements 805 can comprise, forexample, tubes, pipes, or enclosed trusses. The frame elements can bewelded together. In some cases, the frame 801 can be integrally formed.In some cases, the frame 801 and/or portion(s) thereof can be joinedwith other frame(s) in the device/system. In some cases, thermalmanagement fluid flow pathways may be welded or otherwise connected orjoined to one or more portions of the frame structure. For example,external tubing may be joined to one or more fluid inlets or outlets onthe frame 801 or on individual frame element(s) 805). The fluidinlet(s)/outlet(s) may be in fluid communication with fluid flowconduits in frame or frame element(s).

The frame can be of any suitable size or shape. In some cases, the frameis a rectangular box, e.g., comprising any number of vertical andhorizontal frame elements 805 as shown in FIG. 8 . The frame canmechanically and/or structurally support the electrochemical cells in aseries and/or parallel configuration. In some cases, the framepartitions the electrochemical cells into subsets having any number ofcells (e.g., groups of cells as described elsewhere herein). Theelectrochemical cells within a subset can be connected in paralleland/or series. Further, as described in greater detail elsewhere herein,the frame can be joined and/or otherwise connected with other frame(s).For example, groups of cells can comprise (and/or be contained within orsupported by) frames, and the frames can be used to assemble the groupsof cells into larger units. The assembly may include joining of fluidconduits in adjacent frames.

The frame (or any portion thereof) may be configured to interface withthermal insulation. In some implementations, the frame can comprise oneor more specific areas or portions that act as tethering or harnessinglocations for thermal insulation mounting. In some instances, thermalinsulation may be attached to the frame through rigid metallicconnections that may be permanently connected (e.g., welded or bonded)to the frame (or any portion thereof). In other instances, thermalinsulation may be connected to the frame such that the connection pointsare removable or replaceable (e.g., to facilitate service access orperiodic replacement). Thermal insulation may be assembled to the framesuch that the insulation region of the assembly (e.g., a regioncomprising the thermal insulation and/or conduits or connections passingthrough the thermal insulation) does not create a direct thermal pathwaybetween thermally insulated regions (e.g., region comprising a thermalchamber of the device, or a thermally maintained zone of the system) ofthe assembly, and non-insulated regions of the assembly and/or thesurrounding environment.

Implementations of the insulation may include configurations withmultiple layers (see, for example, FIG. 12 ). For example, a thermalinsulation structure (e.g., such as the portion of thermal insulation1200 in FIG. 12 ) may comprise at least about 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 12, 14, 16, 18, 20, 25, 30, 35, or 40 layers. The layers (or anysubset thereof) may be formed of same, similar (e.g., comprisingchemically similar materials, or comprising blends comprising at leastabout 10% 40%, 50%, 60%, 70%, 80% or 90% of a common material) ordifferent materials. In some cases, at least about, about, or less thanabout 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%,70%, 75%, 80%, 85%, 90%, 95% or 100% of the layers in a given thermalinsulation structure are same or similar. In some cases, the layeringmay aid the thermal insulation performance. For example, thin sheets ofair or bonding material between layers may create additional insulatinginterfaces.

The frame can comprise a chamber that contains at least a subset of theplurality of electrochemical cells. The frame or chamber can contain anynumber of electrochemical cells (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more). In some cases, theframe or chamber contains at least about 5, at least about 10, at leastabout 20, at least about 30, at least about 40, at least about 50, atleast about 60, at least about 80, at least about 100, at least about200, at least about 300, at least about 400, at least about 500, atleast about 600, or at least about 700 electrochemical cells. Thechamber can be a thermal chamber. In some cases, the frame or chambercan comprise multiple thermal chambers.

With continued reference to FIG. 8 , the frame can comprise one or aplurality of fluid flow paths. In some implementations, the fluid flowpaths may be parallel. For example, a plurality of parallel fluid flowpaths may be provided. At least a portion of the fluid flow paths may beseparately controllable (e.g., by a control system of the disclosure).Such control may include opening/closing of one or more flow paths,control or maintenance of flow rate(s), control or maintenance of fluidtemperature, etc. For example, a fluid flow rate (e.g., mass flow rate,volumetric flow rate) through at least two of the parallel fluid flowpaths can be separately controllable. The thermal management fluid canenter fluid flow paths, e.g., at 810, through one or more openings. Thefluid can then flow through the frame through any number of (e.g.,orthogonal, parallel) fluid flow paths 805. An individual fluid flowpath may have a cross-sectional geometry that is circular, square,rectangular, oval, or any other suitable shape. The fluid flow path mayhave a cross sectional area of less than about 0.1 cm², less than about0.5 cm², less than about 1 cm², less than about 2 cm², less than about 5cm², less than about 10 cm², less than about 20 cm², less than about 50cm², or less than about 100 cm². The fluid can exit the fluid flowpaths, e.g., at 815, through one or more openings. In an alternativeconfiguration, the fluid can enter the frame at 815 and exit at 810.Further, the fluid can alternatively or additionally enter and/or exitthe frame on any face or boundary of the frame (e.g., on a faceperpendicular or adjacent to the faces/boundaries comprising theinlet/outlet 810 or 815). In some cases, the thermal management fluidenters the frame through a first opening, is divided into a plurality offluid flow paths, and exits through a second opening. In some cases, thethermal management fluid enters the frame through two or more distinctopenings. The thermal management fluid may flow through distinct thermalflow paths (e.g., each in fluid communication with one or more distinctopenings, such as, for example, a distinct inlet and/or a distinctoutlet) that separate the fluid in each path, thus enabling the systemto separately control fluid flow rate through each path (e.g., eachcontrolled by their own fluid flow control actuator, such as, forexample, a life-gate or valve). Such fluid control may be implementedwith the aid of control systems (e.g., system 1100 in FIG. 11 )configured to implement methods of the disclosure.

In some cases, the thermal management fluid does not contact theelectrochemical cells (e.g., the thermal management fluid can beretained within the frame elements). The frame can be made from anysuitable material including plastic, aluminum, steel or stainless steel.The frame can be resistant to corrosion. In some cases, the framecontacts the thermal management fluid and is chemically resistant to thethermal management fluid. The disclosure allows for multiple uses(“multi-use”) of the frame, including, for example, direct contact withthe middle of a hot zone to absorb heat (e.g., pull heat away) from thehottest point in the device/system. In some cases, the thermalmanagement fluid does not come in contact with cells (e.g., therebyincreasing cell life and reducing system complexity). The frame can bechemically resistant to reactive materials (e.g., reactive metals), suchas, for example, reactive metals used in the electrochemical cells(e.g., so that the frame can maintain its structure should one of theelectrochemical cells leak).

The frame can have a feature or characteristic (e.g., geometric feature)that selectively accelerates heat transfer (e.g., the thickness orcomposition of the frame elements and/or the cross-sectional area ordiameter of fluid flow path(s) can be different to allow more or lessheat to pass between the electrochemical cells and the thermalmanagement fluid). For example, a dimension of the frame (e.g.,thickness, cross-sectional area or diameter of a fluid flow path in theframe, or thermal mass of the frame as a whole), or a portion thereof,can be configured to selectively accelerate heat transfer (e.g., inaccordance with location of the frame or frame portion within thesystem). Various geometric features may enable various configurations ofthermal management fluid routing. In some cases, the fluid flow path maybe routed between cells or groups of cells (e.g., between packs) topermit selective removal of heat from the system. In some cases, thefluid may be routed directly onto one or more cell housings (or portionsthereof) or onto frames, interconnections, or other structural or heattransfer members associated with individual cells or groups of cells. Insome cases, the fluid may be routed via a duct, tubing, fins, or otherheat transfer members in contact with one or more cell housings (orportions thereof) or in contact with frames, interconnections, or otherstructural or heat transfer members associated with individual cells orgroups of cells.

The system can be insulated. In some cases, thermal insulation surroundsthe frame (or frame elements) and/or is provided on the inside of fluidflow channel(s). Thermal insulation inside of a fluid flow channel canprovide thermal insulation between the thermal transfer fluid (also“thermal management fluid” herein) and one or more structural portionsof the fluid flow channel (e.g., stainless steel frame). The insulationcan be distributed in a manner that facilitates thermal management ofthe system. An amount (e.g., volume, mass, thickness, total insulatingcapability, etc.) of thermal insulation at or in proximity to (e.g.,facing) the center of the system/device and/or frame (e.g., at or inproximity to a heated zone) may be less than an amount of thermalinsulation at or in proximity to the periphery of the system/deviceand/or frame (e.g., not at or not in proximity to a heated zone, orfacing away from the center). For example, the system may compriseinsulation along at least a portion of a fluid flow path to aid inremoval of heat from a predetermined location within the system. Theamount of insulation along any given portion may vary in accordance withlocation. For example, least amount of insulation may be provided in alocation that is in proximity or adjacent to a heated zone (e.g., theinsulation is thinner in a portion of the fluid flow path adjacent aheated zone of the system, and/or the insulation is thinner in a portionof the fluid flow path that is in the proximity of or adjacent to thecenter of the heated zone, and/or the insulation is thinner in a portionof the fluid flow path that is in the proximity of or adjacent to aspecific group of cells).

FIG. 9 is an example of a distribution of insulation configured toevacuate more heat from the hotter portions of the system than from lesshot portions of the system. As shown, an insulation insert 905 can beplaced into box tubing 910 (having a height (or length) 925 and a width930) to allow more insulation along top and bottom regions 915 of theinside of the tube and less insulation in a central region 920 (e.g., inthe event that there is a thermal gradient across the length (or heightor width) of any thermal management fluid flow pathway). In someexamples, flow paths or channels can be lined with insulation toselectively extract heat from specific locations in the device/system(e.g., the core) to decrease or minimize thermal gradients within thedevice/system, or across a portion of the device/system (e.g., a pack).

In some cases, the system includes ducting. With reference to FIG. 10 ,the ducting 1005 can be located between groups of electrochemical cells1010 (e.g., enclosed by a frame). Thermal management fluid can be passedthrough the ducting (e.g., in addition to or instead of passing thermalmanagement fluid through the frame). The thermal management fluid thatis passed through the frame elements can be the same or different thanthe fluid that is passed through the ducting. Additional ducting can beadded along the edges or the gaps or to pass through the insulation. Insome examples, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18, 20 ormore horizontal, vertical, spiral-shaped, winding and/or other ducts maybe provided.

Fluid ducts, fluid flow paths (e.g., high capacity flow paths and lowcapacity capillaries) and direct fluid contact interfaces can form ahierarchy of heat transfer components/interfaces of various sizes andcapacities (e.g., heat transfer capacities, as determined by fluid flowrate, fluid type, cell housing material, duct material, fluid flow pathmaterial, and so on. Different types of heat transfer components may besuited for different regions or situations (e.g., size of flow pathand/or duct may be configured in accordance with a difference intemperature between the fluid and the cell(s), or a suitableconfiguration may be selected based on operating temperature).

The system can further include a fluid flow system that is configuredand arranged to direct the thermal management fluid through the one ormore fluid flow paths of the frame and/or ducting. The fluid flow systemcan include a pump, a fan, a blower, and/or any other suitable devicefor moving the thermal management fluid. The device used to direct fluidflow can be placed in a cool zone near the inlet of the fluid flow path,near the outlet of the fluid flow path, or inside the hot zone of thesystem and within or peripheral to the fluid flow path. In some cases,the fluid flow system can include multiple pumps, fans, blowers, and/orany other suitable device for moving the thermal management fluidthrough separate fluid flow channels or paths. For example, a pump or afan can be provided for each separate fluid flow path. In anotherexample, fluid may be moved through multiple (e.g., parallel) fluid flowpaths that are in fluid communication with each other by a pump or a fanprovided in or at one of the flow paths; fluid movement through theremaining flow paths may result from the Venturi effect. In some cases,the fluid may be pre-treated (e.g., pre-heated) to prevent thermal shockto the system prior to allowing the fluid to flow in (e.g., prior toadmitting the fluid into) the fluid flow (e.g., cooling) pathways.

In some examples, the fluid flow system can provide separate thermalcontrol over specific or different areas within the hot zone of thesystem (e.g., the system may comprise 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12,14, 16, 18, 20, 25, 30, 35, 40, 50 or more separate control zones). Insome cases, the fluid flow channels can be configured for performingtargeted thermal management (e.g., cooling) of one or more specificgroups of cells (e.g., packs, or a set of packs). Providing thermalcontrol over specific areas within the hot zone may enable the thermalmanagement/control system to make the overall system (e.g., the batteryand/or the system comprising the battery) more isothermal, therebydecreasing or minimizing stresses on the system that may occur due tothe existence of and shifting of thermal gradients within the system.

In some implementations, the fluid flow system operates at all times.For example, if the flow is stopped completely, the fan (an example of acomponent of a fluid flow system) and/or other component(s) of the fluidflow system can overheat and/or melt (e.g., therefore requiring a fanrated for a 550° C. environment). The system may therefore maintain alow volume air flow during idle periods as a buffer (e.g., at the bottomof the device or system (e.g., the core)) to create a slight positivepressure (or over-pressure) inside the fluid flow (e.g., cooling) pathsor tubes, thereby minimizing heat loss through the bottom (or a givensurface) of the system and ensuring that the fan (and/or othercomponent(s) of the fluid flow system) remains cool enough (e.g., stayswithin a specified low temperature zone, or below a given maximum orrated temperature). In some cases, the low volume air flow is providedby the fan.

In some implementations, the fluid flow system operates passively (e.g.,without the need for fans, blowers, or pumps to actively force fluidthrough the fluid flow paths). The movement of thermal management fluidthrough the device or system can be driven primarily by naturalconvection. For example, the system may comprise a valve, damper or‘lift-gate’ component at the inlet and/or outlet of a fluid flow paththat can allow gas or air to flow into and/or out of the heated systemcavity (e.g., thermal chamber). This convective flow process can drivehot air up and out a fluid flow path (e.g., like a chimney) by utilizingthe phenomenon where hot air (or gas) rises and pulls cooler air (orgas) toward the fluid flow chamber. In some cases, natural convection isenabled and/or enhanced by positioning an inlet of the fluid flow path(e.g., the position where the fluid flow path transitions from ambienttemperature, external environment into the hot zone of the system) nearthe bottom of the heated zone (also “hot zone” herein) and bypositioning an exit of the fluid flow path near the top of the heatedzone.

In some examples, the fluid flow system is configured or programmed toprovide the thermal management fluid at an adjustable flow rate that isselected to maintain the temperature of the system or a portion of thesystem at the operating temperature (e.g., between about 150° C. and750° C., or between about 450° C. and 550° C.). The fluid flow systemmay be controlled by one or more computers or processors of (or incommunication with) a management/control system (e.g., the fluid flowsystem may be controlled by a thermal management/control system). Insome examples, the thermal management system and the fluid flow systemare controlled by redundant computers or processors to increase overallsystem reliability.

The fluid flow system may be configured or programmed to provide thermalmanagement fluid to rapidly cool the at least a portion of the system orthe whole system (e.g., the energy storage device or system). Rapidcooling may be required and/or desired in case of an emergency orcatastrophic event (e.g., a catastrophic leak of cell active components,a fire, an earthquake, a flood, etc.) or in case of a scheduled orunscheduled maintenance procedure (e.g., to replace a failing cell orcell pack, a management/control system board and/or other systemcomponent). For example, rapid cooling may be used upon failure orbreach of one or more cells in the system/device (e.g., leading to losthermeticity). Such a failure or breach may be detected by a controlsystem configured to provide thermal management. In some cases, a cellbreach may be small and may result in a gradual degradation of celland/or battery performance over many days or weeks (e.g., 1, 2, 5, 10,15 or 20 days or weeks). In other cases, a cell breach may result in animmediate (e.g., within less than about 1, 5, 10, 30, 40, 50 or 60seconds, within less than about 1, 2, 5, 10, 20, 30, 40 or 50 minutes,within less than about 1, 2, 3, 4, 6, 8, 10, 12, 16 or 20 hours, orwithin less than about one day) degradation in cell and/or batteryperformance and the system may need to immediately stop charging and/ordischarging. In the case of an immediate cell and/or battery performancedegradation due to a cell breach, an emergency cooling procedure may beinitiated, such as, for example, turning on one or more fans/blowersand/or opening valves/lift-gates to accelerate the cool-down process.The fans/blowers in a thermal management system may in some cases onlybe initiated during an emergency cool-down procedure. In some cases, therapid cooling may only be initiated when the temperature of the systemis above a given temperature (e.g., a critical (safety) temperature),such as, for example, the freezing point of the electrolyte (e.g.,molten salts) and/or electrodes (e.g., liquid metals), or above theflammability temperature of a specific active cell material. In someexamples, a critical temperature is greater than about, or about, 550°C., 500° C., 450° C., 400° C., 350° C., 300° C., 250° C., 200° C., 150°C. or 100° C. Rapid cooling may include increasing a flow rate ofthermal management fluid in one or more fluid flow paths of the system.The flow rate may be controlled selectively. At least a portion of suchflow paths may be adjacent to a portion of the system for which afailure or emergency condition is detected (e.g., a failed cell).

An emergency cool-down process may comprise a rapid cool-down procedure.Such a procedure (or method) may be initiated and/or controlled by acontrol system. The method may be used to rapidly cool at least aportion of the energy storage system in response to a potentiallyhazardous event (e.g., earthquake and/or cell breach). The method may beperformed when the system is at a given condition, such as, for example,when the system (or a portion thereof) is at or above (e.g., at leastabout 5° C., 10° C., 20° C., 50° C. or 100° C. above) a given operatingtemperature (e.g., any operating temperature herein), or at or above(e.g., at least about 5° C., 10° C., 20° C., 50° C. or 100° C. above) agiven critical temperature (e.g., a critical freezing temperature). Uponrapidly cooling, a temperature of the system, device, or a portionthereof (e.g., at least one of the electrochemical cells in a battery)may decrease below a given threshold. In an example, the temperature ofat least one of the electrochemical cells may decrease below a freezingpoint of one or more cell components (e.g., a hottest of a plurality ofelectrochemical cells can decrease from its operating temperature to atemperature below a freezing point of the electrolyte). The decrease intemperature may be achieved within a given time period (“time to cooldown”). For example, the cooling may be achieved in less than about 5seconds, 10 seconds, 30 seconds, 45 seconds, 1 minute, 2 minutes, 5minutes, 10 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes, 1hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22hours, 24 hours, 30 hours, 36 hours, 42 hours, or 48 hours. In anexample, a hottest of the plurality of electrochemical cells candecrease from its operating temperature to a temperature below afreezing point of the electrolyte in less than about 4 hours.

At least a portion of the heat that is removed from the system can berejected (e.g., lost) to the atmosphere or environment. In some cases,at least a portion of the heat that is removed from the system can bestored or used in another application (e.g., to heat homes or industrialprocesses through co-generation, or to prevent electronics from beingchilled). In some implementations, a system comprising a circulatoryfluid flow system that is configured to store thermal energy can beprovided. One or more fluid flow paths (e.g., of the device) can be influid communication with a fluid flow path of the circulatory fluid flowsystem. The circulatory fluid flow system can comprise a thermal energystorage medium. The thermal energy storage medium can comprise anysuitable material including, but not limited to, molten salt (e.g., anymolten salt described herein), gravel, sand, steam or water. The thermalenergy storage medium may be stored in a storage reservoir. In somecases, the thermal energy storage medium can be the thermal managementfluid.

Insulation and Thermal Barriers

At least a portion of components of an energy storage device or system(e.g., electrochemical cells, groups of cells such as packs, and frames)may be thermally isolated from other room-temperature components of theenergy storage device or system through thermal insulation boundaries.Thermal insulation can aid in defining thermal barrier(s) that allow oneside of a thermal boundary (e.g., thermal boundary comprising thethermal barrier(s)) to be maintained at or above a temperature suitable(e.g., required) for cell operation (e.g., hot zone), while the otherside of the thermal boundary can be maintained closer to roomtemperature or ambient temperature conditions (e.g., cool zone).

Thermal insulation may comprise materials with known (e.g., high)impedance for heat transfer (also “thermal impedance” herein). Suchmaterials may be packaged in sheets, tiles, wraps, tapes or other (e.g.,similar) form factors such that they may be packaged around the hightemperature zone (also “hot zone” herein). As previously described withreference to FIG. 12 , in some cases, different layers of thermalinsulation may be used in the same assembly (e.g., assembly comprisingthermal insulation assembled to a frame). For example, one layer mayutilize a thermal insulator with a first thermal impedance andsubsequent layers may comprise materials with one or more differentthermal impedances (e.g., a second thermal impedance, a third thermalimpedance, and so on). The thermal insulation may comprise a set orpackage of components. The thermal insulation package can comprise oneor more layers of thermal insulation (e.g., one or more layers ofinsulating material). In some examples, removable and/or replaceablecomponents (e.g., tiles) may be incorporated into the thermal insulationlayers. In some examples, layers that can be displaced by motor or servodrives may be included in or incorporated into the thermal insulationpackage and may be used to help manage the temperature of the system.For example, a control system may activate an actuator (e.g., motor orservo drive) to change the position or configuration of one or moreportions of the thermal insulation package to change (e.g., decrease)the thermal insulating property of the thermal insulation package,thereby increasing, maintaining, or decreasing the rate of heat lossfrom the system. Such a process may be controlled by a control systemand may be part of the thermal management control of the system.

Thermal insulation may have dedicated areas or portions(“pass-throughs”) through which wires, sensors and/or highcurrent/voltage (e.g., cell current or voltage) connections,collectively referred to as “connections” herein, can pass in order toconnect electrochemical cells (e.g., inside the thermal insulation) toother components in the energy storage system (e.g., outside the thermalinsulation). For example, pass-throughs may carry wires and/or sensorsthat are in communication with a management/control system (e.g., system1100 in FIG. 11 ). Such sensors may include, for example, one or moretemperature sensors placed in or in thermal communication with the hotzone of the system. In some examples, pass-throughs carry only voltage(e.g., low voltage) sense wires. The voltage sense wires may be designedto handle (e.g., withstand) only small amounts of current (e.g., lessthan about 10 milli-amperes (mA) or less than about 1 mA). In someexamples, pass-throughs carry voltage sense wires and/or wires fordistributing current to/from cells. In some examples, pass-throughscarry high current and/or high voltage wires to busbars. Pass-throughsmay have a cross-section that is, for example, circular, rectangular,square, oval, or polygonal. Such pass-throughs may have a cross-sectionarea of greater than about 0.0001 square centimeters (cm²), greater thanabout 0.001 cm², greater than about 0.01 cm², greater than about 0.1cm², greater than about 1 cm² or greater than about 10 cm²).

FIG. 12 is an example of a thermal insulation structure portion 1200that comprises a first insulation layer 1205, a second insulation layer1210 and a third insulation layer 1215. A first surface of the firstinsulation layer 1205 can contact or be positioned adjacent a frame (orframe element(s)) 1220 in (or adjacent to) a hot (e.g., inside) zone1225. The frame 1220 can comprise a flow path (e.g., air flow path)1235. A second surface of the first insulation layer 1205 can contact orbe positioned adjacent a first surface of the second insulation layer1210. A second surface of the second insulation layer 1210 can contactor be positioned adjacent to a first surface of the third insulationlayer 1215. A second surface of the third insulation layer 1215 cancontact or be positioned adjacent an outer skin 1230. The outer skin1230 may face a cold or cool (e.g., outside) zone 1240. Thermalinsulation of devices herein may in some cases comprise at least about1, 2, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28,30, 35, 40, 45, 50, 75 or 100 thermal insulation structure portions(e.g., such as the structure portion 1200).

A pass-through (e.g., high thermal efficiency pass-through) 1245provides a conduit from the first surface of the layer 1205, through thelayer 1205, through the layer 1210, through the layer 1215, through theouter skin 1230 to the cold/cool zone 1240. Wires, sensors and/or highcurrent/voltage connections (not shown) may be passed from the hotzone/side 1225 to the cold/cool zone/side 1240.

A pass-through may be thermally efficient to limit or prevent excessiveheat loss through it. In some cases, the pass-through can be filled withmaterial(s) with high thermal impedance to limit or decrease heattransfer from the hot zone of the system to other lower temperatureareas (e.g., to one or more cool zones). The filling material may behomogenous (e.g., one material fills the entire pass-through) orheterogeneous (e.g., two or more different materials are used as fillersin one pass-through). In some cases, the pass-through can comprise oneor more plugs and/or one or more end-caps that may limit or decreaseheat transfer through the pass-through. Plug(s) and/or end cap(s) mayencapsulate material with high thermal impedance within the pass-throughstructure. In some examples, the entire pass-through structure can bemounted on a tile (or sheet, wrap, tape, etc.) of thermal insulationsuch that the tile (or sheet, wrap, tape, etc.) may be removed alongwith the pass-through as part of service or repair.

FIG. 13A is an example of a pass-through 1300 that comprises an end cap1320. The pass-through 1300 can be surrounded by insulation layers 1305,1310 and 1315. Alternatively, the pass-through 1300 can comprise (e.g.,be filled with) filler materials 1305, 1310 and 1315. The pass-throughmay comprise an electrically conductive component (not shown), such as,for example, voltage sense wire(s), high current carrying wire(s), orwire(s) associated with thermal measurement (e.g., thermocouple wires).The insulation layers or filler materials 1305, 1310 and 1315 may bedisposed between a hot zone 1325 and a cold (e.g., room temperature)zone 1340. The end cap 1320 may be attached to a wall or boundary 1330of the pass-through. The wall 1330 may or may not extend along theentire length 1345 of the pass-through. In some cases, the wall 1330 mayextend beyond the last filler material 1315. In such instances, an airgap 1335 may form between the filler material 1315 and the end cap 1320.In some cases, the pass-through may not comprise the wall 1330, and theend cap 1320 may be attached directly to the last filler material 1315;in such a case, the air gap 1335 may or may not form. The end cap 1320can comprise one or more flanges 1350.

The wires that transit the pass-through may comprise special materials(e.g., materials that are stable at or above the operating temperatureof the system, oxidation-resistant materials, materials that havesuitable (e.g., sufficient and/or high) electrical conductivity at theoperating temperature of the system), such as, for example, nickel,aluminum, bronze, brass, stainless steel, or any combination thereof.Such materials may limit or decrease heat-induced corrosion on thewires. The wires in the pass-through may transition (e.g., sequentially)from materials that are stable at higher temperatures, to moreelectrically conducting but less thermally stable materials (e.g.,copper). In some examples, the wire in the pass-through comprises atleast about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25, 30 ormore different sections. The sections may comprise different materials.The sections may be integrally formed, or joined (e.g., welded) togetherto form a composite wire. In some cases, the materials may besequentially arranged in order from materials with highest thermalstability (and, in some cases, lower conductivity) in a region of thepass-through adjacent the hot side to materials with highest electricalconductivity (and, in some cases, lower thermal stability) in a regionadjacent the cool side.

The pass-through may comprise wires that are built into (e.g.,integrally formed with) the pass-through structure. In some cases,different pass-throughs in the system may be designed such that the wirelengths, location of the wires within the pass-through and/or spacingbetween the wires are the same for the different pass-throughs. In somecases, the pass-through may comprise wires that are floating within thepass-through. In some cases, wires may be cast or set in high thermalimpedance material such that wires do not form a straight-lineconnection between high temperature (e.g., hot) and low temperature(e.g., cold/cool, room temperature) zones of the system. Wires routed inthis manner may have excess length incorporated within the pass-throughto allow thermal energy conducted by the wires to be released as thewires travel through heterogeneous layers of thermal impedance materialwithin the pass-through. The (actual) length of the wire may be, forexample, at least about 1.5 times, at least about 2 times, at leastabout 5 times, at least about 10 times, at least about 50 times, or atleast about 100 times greater than a distance from the hot zone to thecold zone (e.g. length of the pass-through). This may aid with easilyand/or safely interconnecting the wires with electronics components,and/or making areas of the system service access/touch safe.

FIG. 13B is another example of the pass-through 1300, further comprisinga wire 1355. The wire 1355 (or multiple such wires) may have acircuitous (e.g., zigzag, spiral or helix) pattern or path (through thepass-through) that can prevent a direct thermal opening from the hotzone 1325 to the cold zone 1340. The rate of heat conducted through oneor more wires in the pass-through may be related to or depend on one ormore of: the temperature difference between the hot zone and the coldzone, the cross-sectional area of the wire(s), the thermal conductivityof the material(s) of the wire(s), and the inverse of the length of thewire(s). In some cases, further reducing the cross-sectional area mayresult in a mechanically fragile wire that is susceptible to breakingand/or oxidation. To reduce the amount of heat conducted through a wire,the wire may have a length that is significantly longer than the lengthof the pass-through. Extra wire loops 1360 may increase the length ofthe wire and reduce the amount of heat that is conducted through thewire. The wire may be configured in a helical coil, such as, forexample, a wire that spirals in a circular geometric path from the hotzone to the cold zone. The axis of the helical structural can be aboutparallel (e.g., substantially parallel) to the direction of the heatflow path from the hot zone to the cold zone. The wire may be configuredin other geometries, such as, for example, a helical-type geometry withan oval, square, rectangular, polygon, and/or other cross-sectionalshape. The heat dissipation may decrease or prevent coupling of heat toelectronics on the cold side (e.g., room temperature zone) 1340.

Pass-throughs may comprise infrared (IR) reflective coatings. The IRcoatings may be applied to pass-throughs to limit or decrease heattransfer through IR losses. In some instances, pass-throughs carryingwires may comprise coatings that reduce abrasion on wire insulation(e.g., wire insulating material) in order to prevent loss of wireinsulation through chaffing.

Pressure Relief Mechanism

FIG. 14 is a cross-sectional side view of an electrochemical cell orbattery 1400 with a pressure relief structure 1411. In an example, thebattery cell 1400 can have an axially symmetric, circular cross-sectionwhen viewed from above (“top view” in FIG. 14 ). The housing 1401 canhave concentric walls 1411 a, 1411 b. A first chamber or cavity caninclude a negative liquid metal electrode 1403, a negative currentcollector 1407, a liquid metal electrolyte 1404, a positive liquid metalelectrode 1405 and a positive current collector 1408. During discharge,a solid intermetallic layer 1410 may form, as described elsewhereherein. The pressure relief structure 1411 forms a second chamber. Thewalls of the first and second chambers can form the concentric walls ofthe housing 1401 which may include a container, as described elsewhereherein. Thus, the pressure relief structure 1411 is provided in theannular chamber (also referred to as “riser pipe” herein) defined by theconcentric walls. In some cases, the concentric walls of the housing maybe integrally formed. Alternatively, the concentric walls may be formedseparately and mechanically joined, e.g., by welding. The housing and/orthe walls can be formed of any materials for housings/containersdescribed herein.

During discharge, the negative liquid metal electrode 1403 can be ananode and the positive liquid metal electrode 1405 can be a cathode. Theintermetallic layer 1410 includes an upper interface 1410 a and a lowerinterface 1410 b. As the lower interface 1410 b of the intermetalliclayer 1410 moves in a downward direction indicated by arrows 1412, theliquid material of the cathode 1405 is compressed. When pressure buildsdue to active electrochemistry in the first chamber space, the cathodematerial can rise between the walls 1411 a, 1411 b of the pressurerelief structure 1411 via one or more openings 1413 a, 1413 b, 1414 a,1414 b. The openings can be provided adjacent to the housing 1401 (e.g.,openings 1413 a, 1413 b) such that the inner wall 1411 a of the pressurerelief structure is not in contact with the bottom wall of the housing1401. In some examples, the bottom wall can be the positive currentcollector 1408. The openings can also be provided at some predetermineddistance from the bottom wall of the housing 1401 (e.g., openings 1414a, 1414 b). For example, the inner wall 1411 a can be attached to thebottom wall of the housing and only have openings 1414 a, 1414 b.

The holes may be circular or of any other shape allowing the cathodematerial to flow through the holes. For example, circular holes may bepreferred to minimize drag on the flowing cathode material. The cathodematerial may flow through the holes as indicated by arrows 1415, andupward in the pressure relief structure as indicated by arrows 1416.

Combinations and/or a plurality of openings 1413 a, 1413 b, 1414 a, 1414b can be provided along the inner wall of the annular pressure reliefchamber 1411. The holes may be provided at different axial distancesfrom the bottom wall of the housing and may be of varying size. Forexample, the holes may be spaced to prevent the intermetallic layer 1410from “bottoming out”, i.e., from reaching the uppermost level of theholes (which may be near the bottom of the first chamber), and blockingthe riser pipe inlet (the area around arrows 1415).

The pressure relief structure can have a top wall 1411 c. The top wall1411 c can close the pressure relief structure to prevent materialinside the riser pipe from spilling over the top of the riser pipe. Insome cases, the wall 1411 b may be formed separately from the housing.For example, the walls 1411 a, 1411 b, and 1411 c can be integrallyformed as an annular tube with a closed top and an open bottom (e.g.,openings 1413 a, 1413 b), or as an annular tube with closed top andbottom but with perforations or holes near the bottom (e.g., openings1414 a, 1414 b). In some examples, one or more parts or all of thepressure relief structure may be formed of one or more materialsdifferent than the housing 1401. One or more parts or all of thepressure relief structure may be formed of an electrically insulatingmaterial, such as the electrically insulating materials describedelsewhere herein.

With continued reference to FIG. 14 , the cathode material in the riserpipe is not in contact with to the electrolyte 1404. Further, thecathode material is electrically isolated from the electrolyte and theanode. When the cathode material is electrically conductive (e.g., aliquid metal cathode material), the cathode material in the riser pipe(second chamber) can be electrically connected with the cathode materialin the first chamber. In some cases, such as, for example, when anunsheathed housing is employed as described elsewhere herein, only thewall 1411 b may be electrically insulating; the walls 1411 b and 1411 cmay be electrically conductive. The wall 1411 c may only be electricallyconductive if it is to not contact the electrolyte at any point.

The cathode material may rise in the pressure relief structure 1411 to aheight h. The height h may vary around the circumference of the pressurerelief structure. The height h can be related to the volume change ofthe cathode (i.e., the liquid and solid cathode materials 1405 andintermetallic layer 1410). For example, the cathode materials 1405 and1410 can have a volume V₁ when charged, and a volume V₂ when discharged.The height h can be related to the volume difference V₂−V₁ and thecross-sectional area of the pressure relief structure. The annularpressure relief structure in FIG. 14 can have a width w, and an arearelated to w and the circumference of the annular structure. Thedimensions of the pressure relief structure, e.g., w, may be such thatthe cathode material can easily enter and rise in the structure. Forexample, the pressure relief structure can be dimensioned to minimizecapillary wicking effects, and to ensure that the cathode materialexperiences minimal drag forces. The pressure relief structure can bedimensioned to accommodate a predetermined amount of cathode material.For example, the pressure relief structure may be dimensioned toaccommodate less than 10%, less than 25%, less than 50%, or less than75% of maximum volume or mass of the cathode material or of the liquidcathode material.

In some cases, the addition of the riser pipe decreases the gap betweena first negative electrode end 1403 a and an adjacent wall (e.g., thewall 1411 a in FIG. 14 ), which may contribute to enhanced side wallcreep of the liquid cathode material. To prevent the cathode materialfrom climbing the pressure relief structure 1411 along the wall facingthe first chamber and shorting to the anode from the sides (i.e.,climbing upward in FIG. 14 , parallel and on the opposite side of thewall 1411 a from the arrows 1416), the pressure relief structure(s) maybe isolated from the anode by a sheath (e.g., carbon or metal nitride orother sheath materials described herein) or coating of material (e.g.,PVD or CVD coating of a high temperature material), which is not readilywet by the cathode material. In some cases, the material may provide asurface texture or chemistry that interacts with the intermetallicmaterial, e.g., the intermetallic may easily slide along the surface.

Conversely, one or more parts of the pressure relief structure, e.g.,the surfaces defining the chamber of the riser pipe, may be formed ofand/or coated with a material that is readily wet by the cathode toensure smooth flow of the cathode material in the riser pipe. Thematerial can be inert. In some cases, the material may have desiredreactivity with the cathode material. In some cases, the inlet and/orthe openings 1413 a, 1413 b, 1414 a, 1414 b can be coated with amaterial that prevents the intermetallic from sliding into the riserpipe. The inlet and/or the openings 1413 a, 1413 b, 1414 a, 1414 b maybe covered with a mesh. The inlet and/or the openings 1413 a, 1413 b,1414 a, 1414 b may comprise one or more valves or valve-like features.For example, the inlet and/or the openings can be configured to allowflow into the riser pipe above a certain hydraulic pressure value (e.g.,during discharging), and to allow flow from the riser pipe into thefirst chamber (e.g., during charging) at a relatively lower pressure.

Alternative configurations of the pressure relief mechanism may includeexternal pressure relief structures, such as, for example, a riser pipemounted externally to the housing 1401 and in fluid communication withthe first chamber via one or more the openings 1413 a, 1413 b, 1414 a,1414 b, ducts or connectors.

Method for Operating an Energy Storage System

The disclosure provides methods for operating an energy storage system.In some cases, the method includes providing an energy storage systemcomprising a plurality of electrochemical cells supported by a framestructure. An individual cell of the plurality of electrochemical cellscan comprise a negative electrode, an electrolyte and a positiveelectrode. At least one of the negative electrode, the electrolyte andthe positive electrode can be in a liquid state at an operatingtemperature of the individual electrochemical cell. The frame structurecan comprise one or more fluid flow paths for bringing a thermalmanagement fluid in thermal communication with at least a subset of theplurality of electrochemical cells. In some cases, the method includesdirecting the thermal management fluid through the one or more fluidflow paths.

The method can be performed to achieve any number of objectives. In somecases, directing of the thermal management fluid is performed tomaintain a temperature of the individual cell or one or more portionsthereof (also “cell parts” herein), a group of cells, or a device orsystem comprising such cell(s) at the operating temperature (e.g.,between about 150° C. and 750° C.). In some cases, directing of thethermal management fluid is performed to increase or maximize theefficiency and/or operating lifetime of the energy storage system.

The thermal management fluid can be directed at a rate that is variedover time. In some examples, the thermal management fluid is directed ata rate that depends on: (a) a temperature of the energy storage systemor electrochemical cell thereof; (b) a rate of change of the temperatureof the energy storage system or electrochemical cell thereof; (c)whether the energy storage system is charging, discharging or idle; (d)an anticipated future operation of the energy storage system; and/or (e)a current or anticipated market condition. The anticipated futureoperation of the energy storage system can include the time and extentof future charging, discharging and/or idle operation of the energystorage system. The current or anticipated market conditions can includethe price of energy.

The thermal management fluid can be directed through the one or morefluid flow paths with the aid of a fluid flow system in fluidcommunication with the one or more fluid flow paths. In some examples,the fluid flow system comprises a vent, damper, lift-gate, valve, fan,pump or convection-assisted flow (e.g., forced and/or naturalconvection).

Heat can be added or removed from the system at any suitable rate. Insome cases, directing the thermal management fluid through the one ormore fluid flow paths dissipates or adds thermal energy from theplurality of electrochemical cells at a rate of about 1 Watt (W), about10 W, about 50 W, about 100 W, about 500 W, about 1 kilo-Watt (kW),about 5 kW, about 10 kW, about 50 kW, about 100 kW, about 500 kW, orabout 1000 kW. In some examples, directing the thermal management fluidthrough the one or more fluid flow paths dissipates or adds thermalenergy from the plurality of electrochemical cells at a rate of at leastabout 1 watt (W), at least about 10 W, at least about 50 W, at leastabout 100 W, at least about 500 W, at least about 1 kilowatt (kW), atleast about 5 kW, at least about 10 kW, at least about 50 kW, at leastabout 100 kW, at least about 500 kW, or at least about 1000 kW. In someexamples, directing the thermal management fluid through the one or morefluid flow paths dissipates or adds thermal energy from the plurality ofelectrochemical cells at a rate of at most about 1 watt (W), at mostabout 10 W, at most about 50 W, at most about 100 W, at most about 500W, at most about 1 kilowatt (kW), at most about 5 kW, at most about 10kW, at most about 50 kW, at most about 100 kW, at most about 500 kW, orat most about 1000 kW.

The temperature of the system or any individual cell thereof can bemaintained with any suitable tolerance. In some cases, upon directingthe thermal management fluid through the one or more fluid flow paths,the temperature is maintained to within less than about 1° C., 2° C., 5°C., 10° C., 20° C., 30° C., 40° C., 50° C., 60° C., 70° C., 80° C., 90°C., 100° C., 150° C., 200° C., or 250° C. of a target temperaturesetting. In some cases, the temperature of an individual cell fluctuatesby at most about 1° C., 2° C., 5° C., 10° C., 20° C., 30° C., 40° C.,50° C., 60° C., 70° C., 80° C., 90° C., 100° C., 150° C., 200° C., or250° C. in a time period of 5 hours or less.

Control Systems, Methods and Algorithms

Provided herein are computer control systems that are programmed toimplement methods of the disclosure. Such a control system (also“system” or “management/control system” herein) can comprise a computerprogrammed to direct a thermal management fluid through one or morefluid flow paths and/or a computer readable medium comprising analgorithm to direct a thermal management fluid through one or more fluidflow paths. Thus, the control system can comprise a thermalmanagement/control system.

In some implementations, the system comprises an energy storage system.The energy storage system can include an electrochemical energy storagedevice comprising one or more electrochemical energy storage cells. Thesystem (e.g., the energy storage system, the electrochemical energystorage device) can comprise a thermal zone (e.g., hot zone). Thethermal zone may contain the electrochemical energy storage cells. Thesystem can further comprise a computer system coupled to the device. Thecomputer system can regulate the charging and/or discharging of thedevice, thermally manage the device, or a combination thereof. Thecomputer system (e.g., controller) can monitor one or more theelectrochemical cells of the system/device a condition indicative of afailure (e.g., breach in a seal of an electrochemical cell of theelectrochemical energy storage device). Such a failure or breachcondition may be used by the computer system to trigger a thermalmanagement response. The computer system can include one or morecomputer processors and a memory location coupled to the computerprocessor. The memory location comprises machine-executable code that,upon execution by the computer processor, implements any of the methodsabove or elsewhere herein. The computer system (e.g., computerprocessor, memory and/or other components of the computer system) arenot in the thermal zone. The computer system may electronicallycommunicate with the thermal zone (e.g., via wires, sensors and/or highcurrent/voltage (e.g., cell current or voltage) connections). In somecases, the computer system may electronically communicate with one ormore components in the thermal (e.g., hot) zone. For example, one ormore temperature sensors (e.g., for monitoring one or moreelectrochemical cells, or for monitoring one or more groups ofelectrochemical cells) may be placed in in the hot zone of the system,and may provide measurement data to the computer system outside of thehot zone. The temperature sensor(s) can be in electronic communicationwith, for example, the computer processor.

In some implementations, the system comprises a plurality ofelectrochemical cells supported by a frame structure. An individual cellof the plurality of electrochemical cells can comprise a negativeelectrode, an electrolyte and a positive electrode. At least one, two,or all of the negative electrode, the electrolyte and the positiveelectrode can be in a liquid state at an operating temperature of theindividual electrochemical cell. The frame structure can comprise theone or more fluid flow paths for bringing the thermal management fluidin thermal communication with at least a subset of the plurality ofelectrochemical cells.

The thermal management fluid can be directed at a rate that is variedover time for any suitable purpose. In some examples, the directing ofthe thermal management fluid is performed to maintain a temperature ofthe individual cell, or cell parts, at the operating temperature. Insome examples, the directing of the thermal management fluid isperformed to increase or maximize efficiency and/or operating lifetimeof the energy storage system. As described in greater detail elsewhereherein, the rate can depend on, for example, a temperature of the energystorage system or electrochemical cell thereof, a rate of change of thetemperature of the energy storage system or electrochemical cellthereof, whether the energy storage system is charging, discharging oridle, an anticipated future operation of the energy storage system, acurrent or anticipated market condition, or any combination thereof.

FIG. 11 shows a system 1100 programmed or otherwise configured tocontrol or regulate one or more process parameters of an energy storagesystem of the present disclosure. The system 1100 includes a computerserver (“server”) 1101 that is programmed to implement methods disclosedherein. The server 1101 includes a central processing unit (CPU, also“processor” and “computer processor” herein) 1105, which can be a singlecore or multi core processor, or a plurality of processors for parallelprocessing. The server 1101 also includes memory 1110 (e.g.,random-access memory, read-only memory, flash memory), electronicstorage unit 1115 (e.g., hard disk), communication interface 1120 (e.g.,network adapter) for communicating with one or more other systems, andperipheral devices 1125, such as cache, other memory, data storageand/or electronic display adapters. The memory 1110, storage unit 1115,interface 1120 and peripheral devices 1125 are in communication with theCPU 1105 through a communication bus (solid lines), such as amotherboard. The storage unit 1115 can be a data storage unit (or datarepository) for storing data. The server 1101 can be operatively coupledto a computer network (“network”) 1130 with the aid of the communicationinterface 1120. The network 1130 can be the Internet, an internet and/orextranet, or an intranet and/or extranet that is in communication withthe Internet. The network 1130 in some cases is a telecommunicationand/or data network. The network 1130 can include one or more computerservers, which can enable distributed computing, such as cloudcomputing. The network 1130, in some cases with the aid of the server1101, can implement a peer-to-peer network, which may enable devicescoupled to the server 1101 to behave as a client or a server. The server1101 can be coupled to an energy storage system 1135 either directly orthrough the network 1130.

The system may comprise a management/control system board (“board”). Theboard can have data acquisition capabilities. For example, the board caninclude a data acquisition board. The board may be able to store and/orprocess data (e.g., the acquired data). For example, the batterymanagement system board may be able to store and/or process the datarather than (or in addition to) converting inputs into digital signals.

The storage unit 1115 can store process parameters of the energy storagesystem 1135. The process parameters can include charging and dischargingparameters. The server 1101 in some cases can include one or moreadditional data storage units that are external to the server 1101, suchas located on a remote server that is in communication with the server1101 through an intranet or the Internet.

The server 1101 can communicate with one or more remote computer systemsthrough the network 1130. In the illustrated example, the server 1101 isin communication with a remote computer system 1140. The remote computersystem 1140 can be, for example, a personal computers (e.g., portablePC), slate or tablet PC (e.g., Apple® iPad, Samsung® Galaxy Tab),telephone, Smart phone (e.g., Apple® iPhone, Android-enabled device,Blackberry®), or personal digital assistant.

In some situations, the system 1100 includes a single server 1101. Inother situations, the system 1100 includes multiple servers incommunication with one another through an intranet and/or the Internet.

Methods as described herein can be implemented by way of machine (orcomputer processor) executable code (or software) stored on anelectronic storage location of the server 1101, such as, for example, onthe memory 1110 or electronic storage unit 1115. During use, the codecan be executed by the processor 1105. In some cases, the code can beretrieved from the storage unit 1115 and stored on the memory 1110 forready access by the processor 1105. In some situations, the electronicstorage unit 1115 can be precluded, and machine-executable instructionsare stored on memory 1110. Alternatively, the code can be executed onthe second computer system 1140. The code can be pre-compiled andconfigured for use with a machine have a processer adapted to executethe code, or can be compiled during runtime. The code can be supplied ina programming language that can be selected to enable the code toexecute in a pre-compiled or as-compiled fashion.

Aspects of the systems and methods provided herein, such as the server1101, can be embodied in programming. Various aspects of the technologymay be thought of as “products” or “articles of manufacture” typicallyin the form of machine (or processor) executable code and/or associateddata that is carried on or embodied in a type of machine readablemedium. Machine-executable code can be stored on an electronic storageunit, such memory (e.g., read-only memory, random-access memory, flashmemory) or a hard disk. “Storage” type media can include any or all ofthe tangible memory of the computers, processors or the like, orassociated modules thereof, such as various semiconductor memories, tapedrives, disk drives and the like, which may provide non-transitorystorage at any time for the software programming. All or portions of thesoftware may at times be communicated through the Internet or variousother telecommunication networks. Such communications, for example, mayenable loading of the software from one computer or processor intoanother, for example, from a management server or host computer into thecomputer platform of an application server. Thus, another type of mediathat may bear the software elements includes optical, electrical andelectromagnetic waves, such as used across physical interfaces betweenlocal devices, through wired and optical landline networks and overvarious air-links. The physical elements that carry such waves, such aswired or wireless links, optical links or the like, also may beconsidered as media bearing the software. As used herein, unlessrestricted to non-transitory, tangible “storage” media, terms such ascomputer or machine “readable medium” refer to any medium thatparticipates in providing instructions to a processor for execution.

Hence, a machine readable medium, such as computer-executable code, maytake many forms, including but not limited to, a tangible storagemedium, a carrier wave medium or physical transmission medium.Non-volatile storage media include, for example, optical or magneticdisks, such as any of the storage devices in any computer(s) or thelike, such as may be used to implement the databases, etc. shown in thedrawings. Volatile storage media include dynamic memory, such as mainmemory of such a computer platform. Tangible transmission media includecoaxial cables; copper wire and fiber optics, including the wires thatcomprise a bus within a computer system. Carrier-wave transmission mediamay take the form of electric or electromagnetic signals, or acoustic orlight waves such as those generated during radio frequency (RF) andinfrared (IR) data communications. Common forms of computer-readablemedia therefore include for example: a floppy disk, a flexible disk,hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD orDVD-ROM, any other optical medium, punch cards paper tape, any otherphysical storage medium with patterns of holes, a RAM, a ROM, a PROM andEPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wavetransporting data or instructions, cables or links transporting such acarrier wave, or any other medium from which a computer may readprogramming code and/or data. Many of these forms of computer readablemedia may be involved in carrying one or more sequences of one or moreinstructions to a processor for execution.

Various parameters of an energy storage system can be presented to auser on a user interface (UI) of an electronic device of the user.Examples of UI's include, without limitation, a graphical user interface(GUI) and web-based user interface. The UI (e.g., GUI) can be providedon a display of an electronic device of the user. The display can be acapacitive or resistive touch display. Such displays can be used withother systems and methods of the disclosure.

Devices, systems and methods of the present disclosure may be combinedwith or modified by other devices, systems and/or methods, such as, forexample, batteries and battery components described in U.S. Pat. No.3,663,295 (“STORAGE BATTERY ELECTROLYTE”), U.S. Pat. No. 3,775,181(“LITHIUM STORAGE CELLS WITH A FUSED ELECTROLYTE”), U.S. Pat. No.8,268,471 (“HIGH-AMPERAGE ENERGY STORAGE DEVICE WITH LIQUID METALNEGATIVE ELECTRODE AND METHODS”), U.S. Patent Publication No.2011/0014503 (“ALKALINE EARTH METAL ION BATTERY”), U.S. PatentPublication No. 2011/0014505 (“LIQUID ELECTRODE BATTERY”), U.S. PatentPublication No. 2012/0104990 (“ALKALI METAL ION BATTERY WITH BIMETALLICELECTRODE”), and U.S. Patent Publication No. 2014/0099522(“LOW-TEMPERATURE LIQUID METAL BATTERIES FOR GRID-SCALED STORAGE”), eachof which is entirely incorporated herein by reference.

Energy storage devices of the disclosure may be used in grid-scalesettings or standalone settings. Energy storage devices of thedisclosure can, in some cases, be used to power vehicles, such asscooters, motorcycles, cars, trucks, trains, helicopters, airplanes, andother mechanical devices, such as robots.

A person of skill in the art will recognize that the battery housingcomponents may be constructed from materials other than the examplesprovided above. One or more of the electrically conductive batteryhousing components, for example, may be constructed from metals otherthan steel and/or from one or more electrically conductive composites.In another example, one or more of the electrically insulatingcomponents may be constructed from dielectrics other than theaforementioned glass, mica and vermiculite. The present inventiontherefore is not limited to any particular battery housing materials.

Any aspects of the disclosure described in relation to cathodes canequally apply to anodes at least in some configurations. Similarly, oneor more battery electrodes and/or the electrolyte may not be liquid inalternative configurations. In an example, the electrolyte can be apolymer or a gel. In a further example, at least one battery electrodecan be a solid or a gel. Furthermore, in some examples, the electrodesand/or electrolyte may not include metal. Aspects of the disclosure areapplicable to a variety of energy storage/transformation devices withoutbeing limited to liquid metal batteries.

It is to be understood that the terminology used herein is used for thepurpose of describing specific embodiments, and is not intended to limitthe scope of the present invention. It should be noted that as usedherein, the singular forms of “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. In addition,unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

1.-20. (canceled)
 21. An electrochemical energy storage system,comprising a thermal chamber comprising a cavity, wherein said thermalchamber is configured to thermally insulate said cavity from anenvironment external to said thermal chamber, and wherein said thermalchamber has a surface area-to-volume ratio of 10 m⁻¹; a plurality ofenergy storage cells disposed in said cavity of said thermal managementchamber, wherein an energy storage cell of said plurality of energystorage cells comprises a negative electrode, a positive electrode andan electrolyte disposed between said negative electrode and saidpositive electrode, wherein said electrolyte and at least one of saidnegative electrode and said positive electrode are in a liquid state atan operating temperature of said energy storage cell, wherein saidenergy storage cell has a surface area-to-volume ratio of less than orequal to about 100 m⁻¹; and a frame disposed in said cavity of saidthermal chamber and configured to support said plurality of energystorage cells.
 22. The electrochemical energy storage system of claim21, further comprising a plurality of heaters disposed in said cavity ofsaid thermal chamber and supported by said frame, wherein said pluralityof heaters are configured to distribute thermal energy throughout saidcavity and maintain said electrolyte and said at least one of saidnegative electrode and said positive electrode in a liquid state. 23.The electrochemical energy storage system of claim 22, furthercomprising a computer system configured to monitor and regulate atemperature of at least a portion of said electrochemical energy storagesystem.
 24. The electrochemical energy storage system of claim 22,wherein said plurality of heaters are configured to maintain said cavityat an operating temperature from about 150° C. to 750° C.
 25. Theelectrochemical energy storage system of claim 21, wherein said framefurther comprises at least one fluid flow path for bringing a thermalmanagement fluid in thermal communication with at least a subset of saidplurality of energy storage cells.
 26. The electrochemical energystorage system of claim 25, wherein said at least one fluid flow path isfluidically separated from said plurality of energy storage cells suchthat said thermal management fluid does not contact said plurality ofenergy storage cells.
 27. The electrochemical energy storage system ofclaim 25, further comprising a fluid flow system that is configured andarranged to direct said thermal management fluid through said at leastone fluid flow path of said frame.
 28. The electrochemical energystorage system of claim 27, wherein said fluid flow system comprises afan or pump.
 29. The electrochemical energy storage system of claim 25,further comprising an actuator configured to direct flow of said thermalmanagement fluid.
 30. The electrochemical energy storage system of claim21, further comprising a fluid flow system that is configured andarranged to direct a thermal management fluid through said cavity. 31.The electrochemical energy storage system of claim 21, wherein saidnegative electrode comprises an alkali or alkaline earth metal.
 32. Theelectrochemical energy storage system of claim 31, wherein said alkalior alkaline earth metal is lithium, sodium, potassium, magnesium,calcium or a combination thereof.
 33. The electrochemical energy storagesystem of claim 21, wherein said electrolyte comprises a salt of analkali or alkaline earth metal.
 34. The electrochemical energy storagesystem of claim 21, wherein said electrolyte is a molten halideelectrolyte.
 35. The electrochemical energy storage system of claim 21,wherein said positive electrode comprises tin, lead, bismuth, antimony,tellurium, selenium, or any combination thereof.
 36. The electrochemicalenergy storage system of claim 21, wherein said energy storage cell ofsaid plurality of energy storage cells further comprises a negativecurrent terminal in electrical communication with the negative electrodeand a cell housing in electrical communication with said positiveelectrode.
 37. The electrochemical energy storage system of claim 36,wherein said negative current terminal is electrically isolated fromsaid cell housing.
 38. The electrochemical energy storage system ofclaim 37, wherein two or more individual energy storage cells of saidplurality of energy storage cells are coupled in series such that saidnegative current terminal of said energy storage cell of said pluralityof energy storage cells is in electrical communication with a cellhousing of at least another energy storage cell.
 39. The electrochemicalenergy storage system of claim 38, wherein said negative currentterminal of said energy storage cell of said plurality of energy storagecells is in electrical communication with said cell housing of said atleast another energy storage cell by a busbar or interconnectioncomponent.
 40. The electrochemical energy storage system of claim 22,wherein said plurality of energy storage cells are configured to provideelectrical energy to said plurality of heaters to operate said pluralityof heaters.